Pennsylvania Flaunts Its Importance

By NATE SILVER

As The New Republic's Nate Cohn has observed, the presidential campaigns - especially Mitt Romney's - have spent conspicuously little in advertising in a state that is traditionally regarded as one of the keys to the election, Pennsylvania.

This could reflect some tactical quirk - one campaign trying to lull the other into a false sense of security, for instance.

But assume for the moment that Mr. Romney's campaign has decided that Pennsylvania is not a fruitful path to electoral victory. Is this a sensible conclusion? Personally, I don't think so.

Pennsylvania won't be the easiest state for Mr. Romney to win. As of Monday, our forecast model gave him only about a 20 percent chance of doing so. And there are some disadvantages to his trying to compete there.

First, it's hard to move votes in Pennsylvania. Between blacks (and college students) in Philadelphia and Pittsburgh on the one hand, and the culturally conservative voters in central Pennsylvania on the other, a lot of the votes there are preordained. There are certainly some swing voters in the Philadelphia and Pittsburgh suburbs, but in general the demographics of the state make turnout there a bit more important than persuasion.

Second, the polls have been more consistent in Pennsylvania than in states like Michigan and Wisconsin. Mr. Obama has led each of the last 16 polls in Pennsylvania, but his margin was in the single digits in all but one of them. Greater consistency in polling also reduces the uncertainty in the forecast.

Nevertheless, our model classifies Pennsylvania as a “tipping point state,” which could conceivably be decisive in the electoral outcome. In fact, it ranked Pennsylvania as the second-most important state as of Monday.

There are two cases in which Pennsylvania could be an important state for Mr. Romney. One case is if he loses Ohio - and th e other if he wins it.

Each day, our model runs a series of Electoral College simulations. Typically, we run 25,001 (the odd number is so that there are no exact ties), but I ran 50,001 on Monday to explore all the different permutations in a bit more depth.

The simulations evaluate the uncertainty in the outcome in each state, and how the states are related to one another. They consider the fact that some states are more similar to one another demographically, and therefore are more likely to move in tandem. They also consider that other factors, like a rising or falling economic tide, is likely to have some effect in all states.

From our set of 50,001 simulations, I looked for cases in which the following conditions held:

1) Mr. Romney won the Electoral College;
2) And, Mr. Romney won Pennsylvania;
3) However, it was close enough that Mr. Romney would have lost the election had he lost Pennsylvania's 20 electoral votes.

That is, thes e are cases where Mr. Romney won with somewhere between 269 electoral votes (an exact tie, but the model resolves most of these cases for Mr. Romney since Republicans are likely to control more delegations in the incoming Congress in the event that the 12th Amendment is invoked) and 288 - and with Pennsylvania in hand.

How often did these cases come up? Not very often - only about 450 times out of the 50,000 simulations, or just shy of 1 percent of the time.

But it's important to consider the context. First, the model sees Mr. Romney as an underdog, albeit not an overwhelming one, to win the election. Second, some of the time that Mr. Romney does win the election, it will be in a blowout.

So, this might seem like a marginal case - but the electoral math matters only at the margin as well. There were only about 4,000 simulations in which Mr. Romney won the Electoral College by such a narrow margin. Compared to that, the 450 cases out of 4,000 in which Pennsy lvania proved to be decisive are not trivial.

I then looked up the most common permutations of wins and losses in each state among these 450 cases. The three most common situations all involved Mr. Romney winning Pennsylvania as a substitute of sorts for Ohio:

How plausible is it that Mr. Romney could lose Ohio but win Pennsylvania? It isn't all that likely: Ohio is typically just slightly Republican-leaning, and Pennsylvania is normally Democratic-leaning by two or three points.

Moreover, the two states have broadly similar demographics - it's hard to move votes in one state without affecting them in the other - something which the model considers.

Still, there's enough uncertainty in the forecast that the case of Pennsylvania proving decisive should not be ruled out.

It's plausible, for instance, that Mr. Romney's opposition to the auto bailout will be more of a disadvantage in Ohio than in Pennsylvania, since the former state relies more on a uto industry jobs. Meanwhile, the new voter identification laws in Pennsylvania could give Mr. Romney an extra point or two there, if they're upheld by the courts.

Mr. Romney will be in fairly bad shape if he loses Ohio. But conditional upon that, Pennsylvania might be his least-bad alternative to pick up the requisite number of electoral votes. Wisconsin and Michigan, for instance, might seem like compelling alternatives - but they are typically a bit more Democratic-leaning that Pennsylvania, and Mr. Romney's polls have been no better in them on the whole.

If Mr. Romney's standing rebounds in Ohio - or if the polls suggesting he's in trouble there are wrong begin with - he could rely on a Keystone-Buckeye parlay. For instance, if Mr. Romney won both Ohio and Pennsylvania, that might suffice for him to win the election despite being swept in the competitive states of the Mountain West, like Colorado and Nevada.

In fact, if Mr. Romney won both Pennsylvania and Ohio, he could afford to lose not just Colorado and Nevada (and New Mexico), but also Virginia. The map you see below is a winning one for Mr. Romney, 273 electoral votes to 265.

In other words, the best defense could be a good offense. If Mr. Romney locks down both Ohio and Pennsylvania, then Mr. Obama obviously has few winning maps.

To be sure, the question of how a campaign ought to allocate its resources is not straightforward. Our model's simulations, I hope, do a reasonably good job of articulating the uncertainty in the forecast, and the relationship in the vote in different states. But they are built from historical data. If the campaigns adopt different tactics than past ones did (for instance, concentrating on a narrower range of states), they could make its empirical analysis less meaningful to the 2012 election.

Still, even if Mr. Romney's campaign has reason to believe that Pennsylvania is not quite at the electoral tipping point, that doe s not necessarily mean that they should pull out of it. Expending some resources there would force Mr. Obama's campaign to do the same. The state is certainly close enough - and it has been important enough historically - that neither campaign can really afford to call the other's bluff.

Interestingly, in the waning days of the 2008 campaign, John McCain's campaign concluded that Pennsylvania was its best shot of defusing Mr. Obama's path to victory, and concentrated many of its resources there. Whether this was a good strategy is hard to say - the McCain campaign had a lot of bad options.

But we're still in July - at least for a few more hours. Adopting such triage strategies is premature, especially in a state that has normally been so important to winning elections.

July 30: Forecast Stays Steady With 99 Days to Go

By NATE SILVER

We crossed the 100-day barrier over the weekend. Americans will decide on their next president on Nov. 6, 99 days from Monday.

Though there have been some interesting developments in polls at the state level, the overall condition of the race remains about the same. President Obama is clinging to a lead of about two points in the average of national surveys, with perhaps a slightly greater advantage in some key swing states.

The national tracking polls continue to be mediocre for Mr. Obama, but on the other hand, some surveys from polling firms that measure the race on a more occasional basis show stronger numbers for him. A Democracy Corps poll released on Monday, for instance, gave him a four-point lead over Mr. Romney nationally, tying Mr. Obama's largest lead in that particular survey. We think that most of the apparent movement in national polls toward or against Mr. Obama in recent weeks likely reflects little more than statistical noise. According to our model, his chance of winning the Electoral College is 66.9 percent as of Monday, little changed from 67.4 percent on Saturday.

Louisiana: Democrats in Registration Only

By NICK CORASANITI

Today, we continue our Presidential Geography series, a one-by-one examination of the peculiarities that drive the politics in all 50 states and the District of Columbia. Today's stop: Louisiana, the Pelican State. FiveThirtyEight spoke with Wayne Parent, a professor of political science at Louisiana State University, and Robert Mann, a professor of mass communication at L.S.U.

When 26-year-old Walker Hines announced that he was switching his party affiliation to Republican from Democrat in 2010, he gave the Republican Party a majority in a Louisiana chamber for the first time since Reconstruction.

The young Mr. Hines's decision was emblematic of Louisiana's political transformation: it had become as red as its famous crawfish.

Much like its Gulf Coast brethren, Louisiana has flipped to a solid red state from a solid blue state over the past 20 years. The most recent FiveThirtyEight projections give Mitt Romne y a 99.7 percent chance of carrying the state, and Republican presidential candidates have carried Louisiana easily since George W. Bush. In 2008, Louisiana was one of four Republican states in the country to vote more in favor of John McCain (58.6 percent) than Mr. Bush in 2004 (56.8 percent).

But while Louisiana votes consistently with the Deep South, its conservative engine is made up of slightly different parts, some of which, when viewed in isolation, falsely appears to make Louisiana more pink, or purple, than red.

Of the roughly 2.9 million registered voters in the state, 1.4 million are registered as Democrats, while about 789,000 are registered Republicans and another 694,000 registered as “other.” Even if every “other” voter sided with the Republicans, it would appear that Louisiana is a hotly contested state. So how is every major state office held by a Republican?

The answer to the deceptive voter regis tration numbers lie, in part, with Louisiana's unique “jungle primary” system used in local, state and congressional elections, but not presidential elections. As in the presidential electoral system in France, all candidates for an office in Louisiana run at once without a separate party-specific primary. If any one candidate receives more than 50 percent of the vote, the election is over. If not, the top two face off in a runoff election a month later. Voters are not required to register with a party to participate in these elections, removing a main incentive for registering with either the Democrat or Republican parties.

“The minimal effort it takes to register with a party just isn't worth it in Louisiana,” Mr. Parent said. “And a lot of older voters who once registered as Democrats, and I'm talking those 50 and over, now vote nearly exclusively Republican.”

In 2008, older voters showed up strong for Mr. McCain, with 65 percent of those in the 50 -64 age range and 69 percent of those 65 and over casting a Republican ballot.

The “jungle primary” system also has the potential to depress voter turnout, which in turn can lead to misleading exit polls and even some occasional surprise upsets. When voters are forced to return to the polls in the case of a runoff, many won't come back if the issues that had initially drawn them to the polls were already decided.

“Say there was a hotly contested congressional primary that was decided in the first election, and then a lot of local bills and state races went to a runoff, I don't think many people would be coming back out to the polls,” Mr. Parent said.

Electoral system aside, Louisiana became a Republican stronghold because of one main demographic that has shifted through the years: the Catholic vote.

Louisiana has a large Catholic population, setting it apart from its Gulf Coast neighbors. In the 2012 Republican primary, Catholics made up 36 pe rcent of the voters in the primaries. While Catholics weren't tallied in Mississippi or Alabama exit polls in 2012, they accounted for only 8 percent in Mississippi and 5 percent in Alabama in 2008.

The Catholic vote is strongest in the predominantly Cajun southwestern part of the state known as Acadiana. Catholic voters once made up a large part of the “swing” vote in Louisiana, before social issues like abortion and same-sex marriage became part of the political conversation. In 1992, 41 percent of all voters in the state identified themselves as Catholics, and 47 percent of Catholics voted for Bill Clinton. By 2008, the vote had switched, with 70 percent of Catholics voting for Mr. McCain.

“Cajun Catholics are no longer moderately swing votes at all,” Mr. Parent said. “They are becoming as reliably Republican as Southern Baptists.”

However, this is not to say that the other regions of Louisiana hold no sway over elections. As FiveThirtyEight explained in its primary breakdown of Louisiana's political geography, the northern region of Louisiana is regarded as the most conservative region of the state, essentially behaving electorally as an extension of the states it borders: Arkansas to the north and Mississippi to the east. The southeastern part of the state tends to be evenly matched. While New Orleans and Baton Rouge are the state's Democratic strongholds, the surrounding suburbs are some of the most consistently Republican areas in the state.

The Bellwether: De Soto Parish

In the northwest corner of the state, south of Shreveport, De Soto Parish best reflects the current and continuing shift to the right of Louisiana. It has voted within three percentage points of the state margin in each of the last three presidential elections. It has a slightly larger black population (40 percent) than the state as a whole (32 percent), and with its proximity to Shreveport, has a blend of suburban Republican i deologies with Southern Baptist social conservatism.

The Bottom Line

Mr. Romney doesn't need to pick Gov. Bobby Jindal as a running mate to win Louisiana's eight electoral votes. The state will be called for the Republican candidate mere seconds after polls close on Nov. 6. Any Democratic hopes for winning the state disappeared in the 1990s.

And major disasters in the state have only kicked the Democrats further down. In response to the Deepwater Horizon oil spill, President Obama placed a moratorium on drilling in the Gulf of Mexico, which created a sense of resentment toward the president in Louisiana, said Mr. Mann, a professor of mass communication at L.S.U.

“I don't hear anyone talk as bad about BP as they do about the moratorium,” he said. “People in Louisiana, Democrats and Republicans, saw it as an intrusion into their way of life.”

Where the oil spill brought resentment, Hurricane Katrina brought devastation. New Orleans lost 14 0,845 residents, a drop of 29 percent from 2000 to 2010. The majority of that loss can be attributed to the storm. The decrease in population was also a reason for Louisiana's losing a Congressional seat and an electoral vote in 2012.

“Katrina really did accelerate a lot of the changes that we have seen come about, like the Republican control of every statewide elected office,” Mr. Mann said. “The shift to the right was already occurring, but Katrina may have been the tipping point.”

One of Apple\'s Best Ideas Ever - Made Worse

I think the MagSafe connector is one of Apple's best ideas ever. It's on the end of every Mac laptop's power cord. It attaches to the laptop with a powerful magnet-but if anybody trips on it, it detaches and falls harmlessly to the floor. The laptop doesn't go crashing down with it.

In this year's laptops, though, like the MacBook Air and the 15-inch Retina display MacBook, Apple changed the design of the MagSafe connector to make it skinnier. Everyone who'd bought a bunch of power adapters for their old Apple laptops has to buy a $10 adapter for each one of them to make it fit the new laptops.

But that's not the worst of it.

The beauty of the MagSafe connector was that Apple had found precisely the right balance between attachment and detachment. Strong enough to hold the connector in place, weak enough to detach if it gets yanked.

The MagSafe 2 connector fails that balance test. Badly. The magnet is too weak. It's so wea k, it keeps falling out. It falls out if you brush it. It falls out if you tip the laptop slightly. It falls out if you look at it funny. It's a huge, huge pain.

That weakness is compounded by a second problem: a return to the “T” design of older MagSafe connectors. In other words, this thing comes straight into the side of the laptop - the cable shoots out at 90 degrees - instead of hugging the side with the cord parallel, like the old “L” connectors. As a result, it protrudes a half inch beyond the left edge. You can't rest the left side of the laptop on your thigh. It's constantly getting bumped. And since the magnet has all the grip strength of an elderly gnat, guess what happens?

I bought a MacBook Air for myself last month. It's my main machine - I'm on this thing many hours a day - so I spent the huge bucks and loaded it up with memory and storage. And I'll tell you, as a laptop, it's a dream. It's by far the fastest laptop I've ever used. It start s up in a matter of seconds. Even Photoshop loads quickly. I routinely keep 15 apps open simultaneously, and I can flip between them without ever having to wait.

But the poorly designed MagSafe connector is infuriating. It's the worst Apple design blunder since the hockey-puck mouse.

Some of the customers on the Apple Store Web site (who give it, cumulatively, a 1.5-star rating), suggest buying the older MagSafe power adapters and equipping them with the $10 adapter, which they say grips the laptop better. Unfortunately, that's a big expense, it creates an even bigger protrusion from the left side, and the tiny adapter is easy to lose.

Others are just exasperated. “I find myself trying to think of a workaround,” says one of the unhappy customers on the Apple store Web site. “Glue? No. Binder clip? No. Duct tape? Maybe. Stupid design.”

I'm with you, brother. Say amen and pass the duct tape.

Which Olympic Records Get Shattered?

By NATE SILVER

In track and field, athletes compete not just against one another, but against the intrinsic barriers of human achievement. At the London Olympics, the runners and jumpers and javelin-throwers will set fewer world records than the swimmers. But the ones they do set are more likely to survive the test of time. Read more in the Sunday Review.

July 28: Missouri Slipping Away From Democrats

By NATE SILVER

Missouri, the state that was once considered the nation's ultimate bellwether, looks as though it is likely to be out of reach for President Obama this year, unless there is a significant shift toward him in the final 100 days of the campaign.

A Mason-Dixon poll of the state, released on Saturday, gave Mitt Romney a nine-point lead there. Mr. Romney's nine-point lead matches his advantage from another poll of the state, conducted by the firm We Ask America, which was released earlier this week.

The forecast model now estimates that Mr. Romney has an 88 percent chance of winning Missouri in November. And Missouri has fallen off the list of tipping point states, meaning that it is very unlikely to be a decisive state in determining the winner of the Electoral College. The cases where Mr. Obama wins Missouri are probably those where he is headed toward some sort of near-landslide in the national race, like because of an une xpected rebound in the economy.

Democrats have made gains in some parts of the country in recent years - most notably in the Mountain West and in Virginia, which has increasingly begun to behave as a Northern state. But they have receded in the poorer states of the upland South, like Missouri, Arkansas, Kentucky, Tennessee and West Virginia.

With the exception of a few urban centers like Knoxville, Tenn., these regions have always been culturally conservative. But they also once had a reputation for being economically moderate or even populist, tending to support elements of the welfare state.

In the past four presidential elections, political partisanship has become more uni-dimensional, with a higher percentage of voters tending to align with the same party on both economic and social issues - even though there is often little intrinsic relation between them. In this part of the country, the trade seems to have worked against Democrats - or at least it ha s worked against the fairly liberal Democrats who have been the party's presidential nominees in the past four election cycles.

Over all, Mr. Romney's chances of winning the Electoral College improved somewhat in Saturday's forecast, to 32.6 percent from 30.9 percent on Friday, according to the model.

One reason for Mr. Romney's improvement - in addition to his strong Missouri poll - was that we went back and double-checked our polling database for cases in which polling firms had reported both registered voter and likely voter results within the same survey release.

A comparison between these numbers forms the basis of the forecast model's likely voter adjustment, which shifts numbers from polls of registered voters toward Republican candidates since Republicans typically perform better on surveys that estimate how likely each voter is to actually participate in the election.

The model shifts registered voter polls toward the Republican candidate by 1.5 percentage points as a default, since this is the average change from previous presidential election years. But the adjustment can increase or decrease as additional data becomes available. Based on the data so far this year, the model now estimates that the shift will be slightly larger than average this year, equal to about 2.3 percentage points instead.

July 27: Ohio Polls Show Trouble for Romney

By NATE SILVER

I wrote earlier this week about some of the challenges in comparing state polls and national polls. Sometimes, apparent differences between the two sets of numbers can result from methodological quirks of the polling firms that are active in each arena, as well as random sampling error.

With that said, we are starting to see a bit of a gap between our Electoral College and popular vote forecasts based on the latest polling data this week - one which potentially favors President Obama.

In general, the polls from nonswing states this week, ranging from New Jersey to North Dakota, were mediocre for Mr. Obama. But his numbers held up better in swing states.

Nowhere was this more apparent than in Ohio, where there were two new polls out on Friday. One of them, from the firm We Ask America, gave Mr. Obama an eight-point lead there. Another, from Magellan Strategies, put Mr. Obama up by two points.

Our model thinks the Magellan Strategies poll is a more realistic estimate of the state of play in Ohio. The model now forecasts a three-point victory for Mr. Obama there, which it translates to about a two-in-three chance of his winning the state given the uncertainty in the forecast.

Mr. Obama's projected three-point lead in Ohio is important for the following reason, however: it's slightly larger than the 2.4-point advantage that the model now gives Mr. Obama in the national popular vote.

In other words, based on the data so far this year, Ohio has been slightly Democratic-leaning relative to the country as a whole. That reflects a reversal from the usual circumstances. Normally, Ohio - though very close to the national averages - leans Republican by two points or so.

A split between the winners of the popular vote and the Electoral College is still relatively unlikely, in the view of the model. There is only a 3.9 percent chance that Mr. Oba ma will win the Electoral College but lose the popular vote, it estimates.

However, the model now assigns just a 1.3 percent chance to the reverse happening: Mr. Romney's winning the Electoral College while losing the popular vote.

Ohio is a big part of the reason. It's by no means impossible that Mr. Romney could win the Electoral College despite losing Ohio, but it would be an uphill battle.

If Mr. Obama won all the states that John Kerry did in 2004, and Ohio, he would have 264 electoral votes.

Winning New Mexico in addition to these states, where Mr. Obama is heavily favored, would make the Electoral College a 269-269 tie. That isn't necessarily a problem for Mr. Romney. The incoming House of Representatives is likely to contain a majority of Republican delegations, which would presumably vote for him under the 12th Amendment.

However, if Mr. Obama claimed any other competitive state that Mr. Kerry lost - Nevada, Iowa, Virginia, Florida or C olorado, for example - he would win the Electoral College outright, regardless of what happened in New Mexico.

Of the states, Nevada is probably the most problematic for Mr. Romney. He has trailed in all the polls there, and it has increasingly begun to behave as a Democratic-leaning state.

Another plausible scenario is that Mr. Romney could win New Hampshire, which Mr. Kerry lost in 2004, but lose New Mexico and Nevada. In that case, he'd lose the Electoral College by two votes, with 268 electoral votes to Mr. Obama's 270.

Alternatively, Mr. Romney could try to win one of the Midwestern states that Mr. Kerry won - most likely, Pennsylvania, Michigan or Wisconsin. But these states have broadly similar demographics to Ohio, and it is unlikely that Mr. Romney would win them conditional upon losing the Buckeye State.

Although state economic statistics have only modest predictive power as compared with the national numbers, Mr. Obama may be benefiting fro m the fact that Ohio's unemployment rate has fallen substantially - to 7.3 percent from a peak of 10.6 percent. Had the national unemployment rate declined by a similar margin, Mr. Obama would likely be a clear favorite in the election right now.

Much of the gain in Ohio has been from auto industry jobs, a relative bright spot in the economy, and a potential problem for Mr. Romney since he opposed the federal bailout of the major auto makers.

Mr. Romney could seek to even the score by naming Senator Rob Portman of Ohio as his vice-presidential nominee. Vice presidents do not make as much difference as the conventional wisdom sometimes holds: a net gain of two points by appointing a home-state candidate is a roughly realistic estimate, although it can vary a lot from case to case. Still, gaining two points in Ohio would provide a pretty meaningful push to Mr. Romney given the way that the polls look right now.

Mr. Obama also benefited on Friday from the rise in the stock market, which improved the model's economic index. The S. & P. 500 closed at 1,386 points on Friday, its highest figure since May.

The stock market is likely to remain volatile in the weeks ahead, as investors seek to weigh the consequences of critical economic news - including next Friday's jobs report, possible actions by the Federal Reserve to stimulate the economy and efforts by the European Central Bank to defend the euro zone.

My personal read on the stock market is that it seems to be pricing in a fairly high likelihood of stimulative actions by central banks, both in the United States and Europe. If investors do not get what they are hoping for, it could decline significantly.

In the meantime, Mr. Romney's campaign will need to consider whether it trusts the polls showing him down in Ohio, and if so, what actions it might take to remedy that problem.

What the New G.D.P. Figures Mean for the Election

By NATE SILVER

Let me begin with an important reminder. Unless you have a particular interest in economic or political forecasting, the major upshot of Friday's gross domestic product report, which estimated that the economy grew at an annualized rate of 1.5 percent in the second quarter, is simply that the American economy is still not doing very well.

What economists call “trend” or average growth is supposed to be closer to 3 percent. Moreover, after many past recessions, we've had above-trend growth in the year or so after the recession to help make up for the lost productivity in the economy.

We didn't have that this time around. After the latest revisions to the data, only two quarters since the recession officially ended came in above that 3 percent threshold; all the others were below it.

So, there remains an output gap of about $800 billion dollars. That's the difference between what economists think annual G.D.P. wo uld be if the economy were at its full productive capacity, and what it actually is.

But we concern ourselves with the more narrow question of election forecasting at this blog. On that front, I agree with other analysts who suggest that the G.D.P. numbers don't contain all that much new information.

In the case of how our forecasting model is designed, this is true - it does not use the backward-looking G.D.P. numbers.

The reason for this is simple: G.D.P. is reported on a quarterly basis. That's a bit slower than we'd like, when there are other good data series that have a shorter lead time.

Moreover, the initial estimates of G.D.P. are often very noisy. It's possible that Friday's numbers will eventually be revised to show that growth was actually negative, meaning that the economy was potentially in recession. It's also possible that they'll eventually be revised upward to show 3 percent growth or better. It's very com mon to see quarterly G.D.P. numbers revised by a full percentage point in one direction or the other, and reasonably common for the adjustments to be larger than that.

Instead, the bulk of our economic index (60 percent of the weight) is assigned to a series of four monthly indicators that correlate reasonably well with G.D.P. over the long run, and that economists use to help date recessions and recoveries.

These numbers are noisy too, of course - some more so than others. (The series called personal income, for instance, tends to get especially substantial revisions, while the jobs numbers are a bit more stable.)

But if you look at what they say in combination with one another, you can usually get a reasonably good estimate of G.D.P. a couple of months before the figure is released.

That was the case here. The reported figures of 1.5 percent growth in the second quarter, and 2 percent growth in the first quarter, are consistent with what the economi c index had already “priced in” to its expectations.

The chart below shows the normalized figures for the four G.D.P. proxies: payroll jobs, industrial production, personal consumption and personal income. The normalization process translates these numbers so that they are on the same scale as one another, and the same scale as quarterly G.D.P. reports.

The four indicators tell different stories about the economy. Income growth has been very poor, for example, while industrial production has been pretty encouraging.

For better or for worse, this is a pretty normal state of affairs. Economic data is really noisy, and different series often diverge quite a bit, especially before revisions.

Still, if you average the four numbers together, you get an index of 1.7 percent growth. That almost exactly matches the G.D.P. growth rate during the previous six months, which is the period that our model is mostly concerned about.

Growth at this rate woul d ordinarily make a president's re-election prospects extremely tenuous: probably about 50-50, according to our model and others.

The reason our economic index sees Mr. Obama as a very modest favorite for re-election is because it also considers inflation, which is assigned 15 percent of the weight. And inflation has been very low.

Imagine the counterfactual: that on top of all the other problems in the economy, we also had, say 6 percent inflation. Then gas might cost $4.75 a gallon, and you'd notice the change in prices pretty frequently when you went to the grocery store. Under those circumstances, our model would have Mr. Obama as an underdog.

Of course, the G.D.P. numbers and other economic statistics are pretty tenuous on their own. If things get much worse than this in the next three-and-a-half months before the election, our economic index will start to see Mr. Obama as an underdog even with the low inflation rate.

New York: Not as Blue as It Could Be

By SARAH WHEATON

Today we continue our Presidential Geography series, a one-by-one examination of the peculiarities that drive the politics in all 50 states and the District of Columbia. Today's stop: New York. FiveThirtyEight spoke with Steven A. Greenberg, the Siena College pollster and political consultant, and Bruce Gyory, a consultant at Corning Place Communications and an adjunct professor of political science at the University at Albany.

New York's Democrats are underachievers.

Sure, Barack Obama won the 2008 election in New York with 62.2 percent of the vote â€" behind only Hawaii, Vermont and Washington, D.C. â€" and Andrew M. Cuomo took the governor's mansion in 2010 with 62.6 percent.

But in a state where almost half of the voters are registered Democrats, giving them a 2-to-1 advantage over registered Republicans, is that really such an accomplishment?

To understand the state's politics, it makes sense to divide New York into three regions: New York City, the downstate suburbs (Nassau and Suffolk Counties on Long Island, Westchester and Rockland Counties just north of the city), and the sprawling, diverse upstate region.

As far as Democratic performance goes, New York City, the state's liberal economic engine, is the biggest slacker of all. A city that has not voted for a Republican for president since Calvin Coolidge in 1922 has not elected a Democratic mayor since 1989. The five boroughs also don't vote their weight: As Mr. Gyory notes, in 2008 New York City made up about 42 percent of the state's population, 38 percent of its registered voters and 34 percent of the vote â€" and that figure actually shows improvement over previous years.

Upstate New York, on the other hand, contributes 42 percent to 46 percent of the vote, despite having about 36 percent of the population and 39 percent of the registered voters, Mr. Gyory said. The region includes vast rural tracts, including the northernmost stretches of Appalachia, as well as dying manufacturing towns and the state's capital. Upstate's medium-size cities, like Rochester and Buffalo, fit a Rust Belt profile â€" people even say “pop” instead of “soda.”

“A Democrat has a problem if he or she cannot carry at least 40 percent of the vote upstate,” Mr. Gyory said. But 45 percent, he added, can almost guarantee a victory.

It's hard to blame New York's Democrats for resting on their laurels. The last time a Republican presidential candidate won the state was Ronald Reagan's landslide re-election in 1984, and the last Republican to win a statewide race was Gov. George Pataki, whose third re-election race was two decades ago.

With the careers of Mr. Pataki and Rudolph W. Giuliani apparently over, the New York Republican Party has no standard-bearer. Republicans' small registration numbers hamper their ability to draw in undecided voters, because the conservative primary electorate tends to choose candidates well to the right of the state's mainstream.

“It's getting bluer because the Republicans are not giving them much of a run for their money,” Mr. Gyory said.

Case in point: In 2010, an energized Tea Party-infused Republican electorate chose Carl P. Paladino, a Buffalo businessman known more for his eccentricity than for his political acumen, over former Representative Rick A. Lazio of Long Island. (Earlier in the campaign, the head of the state Republican Party was so despondent about the party's chances that he tried to recruit a Democrat to switch parties and run against Mr. Cuomo on the Republican ticket.)

Mr. Cuomo beat Mr. Paladino by almost 30 points, and the state's Democratic United States senators won by similar margins. But as Mr. Greenberg pointed out, the Democrat running for attorney general won by 11 points, and Thomas P. DiNapoli won re-election to the comptroller's of fice by only 2.5 points.

“So we clearly have swing voters,” Mr. Greenberg said.

But without moderates, Republicans might not be able to draw them in.

“In gubernatorial years, New York is a Democrat, not a liberal, state,” Mr. Gyory said. But he warns that if Republicans “continue to not run good candidates, they won't be able to take advantage of that distinction.”

The Bellwethers
According to Mr. Greenberg, even the “worst Democrat” would get 40 percent of the vote, and his or her terrible Republican rival would get about 25 percent. An additional 15 percent of voters are likely to favor Democrats in most cases, he said, so only about 20 percent of the electorate is truly up for grabs.

Where do these swing voters live? Westchester County is a key battleground. Immediately north of New York City, Westchester is one of the most ethnically diverse counties in the state, with growing Hispanic and Asian communities clustered in cities like Yonkers and New Rochelle. Efforts to integrate minorities into the county's graceful, affluent bedroom communities along the Hudson River with affordable-housing grants have caused tension, and the moves have put County Manager Rob Astorino â€" one of the few rising Republican stars â€" in the spotlight.

Mr. Greenberg looks to Westchester and to Erie County, where Buffalo is situated, to determine a Democrat's chances.

“As a Democrat, you do what you're supposed to do in the city, you carry Westchester and Erie, you're going to win,” he said. Republicans have a more daunting task.

“If a Republican is going to be competitive in New York State, they've got to carry the suburbs, they've got to carry upstate,” Mr. Greenberg said. Republicans don't have to win upstate by a high margin, he added, but they need to amass “close to 60 percent” in the suburbs.

That's likely to be increasingly difficult. Though they once leaned Republica n, Long Island's two counties are increasingly purple. Almost a third of Long Island's population is nonwhite, a dramatic shift. In Westchester, that figure is 35 percent.

The other suburbs around Albany, Rochester, Buffalo and Syracuse are also competitive, and there are even some swing voters in New York City, including the white ethnic enclaves of the boroughs outside Manhattan, including Staten Island, which is home to the First Congressional District, one of the most fiercely contested in the state.

The Bottom Line
Making matters worse for Republicans, people from the state's more liberal areas are moving upstate. Northern Westchester through the northern Saratoga Valley, along the Hudson, has the state's highest rate of growth, according to Mr. Gyory. Many of the migrants are coming from New York City, drawn in particular by an emerging high-tech sector. (Mr. Obama visited the University at Albany's College of Nanoscale Science and Engineering in May.) The result, Mr. Gyory said, resembles “what's going on in North Carolina - it's less predictably Republican than it was.”

This isn't to say that there are no Republican bastions. On the contrary, Republicans hold a majority in the State Senate, with upstate's many rural districts sending conservatives to Albany.

“Democrats can't win upstate outside of major urban areas,” Mr. Greenberg said. And down the ballot, “most of upstate is actually in play,” he said.

A shrinking population cost New York two House seats, bringing the number to 27. When it appeared that his district would be split, one upstate Democrat retired, and several of the redrawn districts incorporated greater shares of Republicans. But the Republican candidates will not have much help from the state and national parties. “They're not going to contest for the presidential; they don't have a strong Senate candidate,” Mr. Gyory said. “They don't give a lot of air cover down -ballot.”

As minorities and young people move to swing districts, and as New York City begins to vote more in proportion with its share of the population, the long-term trends don't look good for Republicans. But New York's cycles are slow.

“In New York, the party pendulum doesn't swing in four- and eight-year cycles,” Mr. Gyory said. “It tends to swing in 16-to-20-year cycles.”

July 21: Polls Show Forward Movement for Obama in Florida

By NATE SILVER

As we mentioned last week, President Obama's polling has been holding up reasonably well in Florida. The latest example was a SurveyUSA poll, released late Friday, that showed him five points ahead there among likely voters.

SurveyUSA is a strongly rated pollster. It includes cellphones in its sample, which made a fair amount of difference in this poll; Mr. Obama trailed by six points among land-line households. And it gives its respondents the option of completing the interview in Spanish.

Still, because Florida has received plenty of polling - and because SurveyUSA's polls have been somewhat Democratic-leaning so far this cycle - the poll does not make too much difference in our forecast. Mr. Obama's chances of winning Florida improved to 52 percent from 49 percent, according to our forecast model. If you're determined to “call” each state, it technically flipped from red to blue. But if you look at the election probabilistically, as we do, these results are about the same.

Nevertheless, there had been earlier points when our model gave Mr. Obama no better than about a one-in-three chance of carrying Florida this November. As the results have closed there, it has moved up our chart of tipping-point states that are most likely to determine the election, and is now in an essential three-way tie with Pennsylvania and Virginia for second place on the list of the most important states. (All of these states rank below Ohio.) That means that as expensive as it is to run for office in Florida, it will, as usual, be a state that neither campaign can afford to take for granted.

State and National Polls Tell Different Tales About State of Campaign

By NATE SILVER

The United States of America is a constitutional republic made up of 50 states and the District of Columbia.

I'm sure you knew that. But it seems as though pollsters might have slept through social studies class. In theory, state polls and national polls must ultimately agree with each other: the whole must equal the sum of the parts. In practice, they leave a different impression about the state of the presidential race.

Consider that as of Tuesday afternoon, President Obama's lead in the RealClearPolitics average of national polls was 1.3 percentage points over Mitt Romney.

But Mr. Obama led by a mean of 3.5 points in the RealClearPolitics averages for the 10 states (Ohio, Virginia, Florida, Pennsylvania, Colorado, Iowa, Nevada, Michigan, New Hampshire and Wisconsin) that are most likely to determine the election outcome, according to our “tipping point index.” If the list is expanded to cover the five other marginally competitive states where RealClearPolitics calculates a polling average - Arizona, Minnesota, Missouri, New Mexico and North Carolina - Mr. Obama's lead averages 3.1 points, according to the numbers.

While that isn't an enormous difference in an absolute sense, it is a consequential one. A one- or two-point lead for Mr. Obama, as in the national polls, would make him barely better than a tossup to win re-election. A three- or four-point lead, as in the state polls, is obviously no guarantee given the troubles in the economy, but it is a more substantive advantage.

The difference isn't an artifact of RealClearPolitics's methodology. The FiveThirtyEight method, which applies a more complicated technique for estimating polling averages, sees broadly the same split between state and national polls.

Or if you prefer a bare-bones approach, you can take a count of the polls conducted in swing states: how many show leads for Mr. Obama, and how many put Mr. Romney on top?

In polls from the top 10 tipping point states since June 1, Mr. Obama has led by any margin in 43 surveys, while Mr. Romney has held the lead in nine of them.

Since July 1, the discrepancy has been even clearer: Mr. Obama has held leads in 19 polls from these states, and Mr. Romney two.

Often, Mr. Obama's leads in these polls have been small, but that still doesn't seem consistent with the notion - as the national polls seem to express - that the race is about tied. We need some way to explain the results, or at least a strategy to deal with the uncertainty this introduces.

Perhaps the most common assumption is that if Mr. Obama is performing comparatively well in swing state polls, he might have some advantage in the Electoral College in relation to the national popular vote. Perhaps we are on track for a split outcome, as we had in 2000, but this time with Democrats benefiting from the idiosyncrasies of the Electoral College.

It's certainly possible that we'll see such an outcome, but historically speaking, it is not something you would want to bet on. Besides 2000, such a split occurred just two other times - in 1876 and in 1888 - since the popular vote came to be widely reported. That's just 6 or 7 percent of the time. The FiveThirtyEight model thinks the odds of such a split are not much better than that this year.

Instead, there are two other hypotheses that might also explain the difference, in whole or in part. They are banal and even boring, so simple that they might be overlooked.

One of these hypotheses is that the state polls are overrating Mr. Obama somehow. The other is that the national polls are underrating him. Or it could be that both of these ideas are right to a degree, and the truth lies somewhere in the middle.

In this column, I will describe a method for comparing state and national polls: they are more suitable to a direct comp arison than you might think. On Wednesday, we'll return to the question of how to derive the best prediction of the election outcome from the two sets of numbers.

***

The reason that state polls and national polls are fairly easy to compare is that the relative order of the states is extremely consistent from year to year. We know more or less how Vermont, Iowa and Wyoming, along with the other 47 states, will line up relative to the national trend.

Let's define a simple quantity called the relative popular vote. It measures the popular vote in a given state relative to the national popular vote.

For instance, in 2008, Mr. Obama won Ohio by 4.6 percentage points. But he won the national popular vote by a slightly wider margin, 7.3 points. Subtracting 7.3 points from 4.6 yields negative 2.7. That means that Ohio was slightly Republican-leaning - by 2.7 points - relative to the national trend.

Knowing what the relative popular vote had been in eac h state in 2004 would have sufficed to explain about 90 percent of its relative popular vote in 2008, even without consulting any polls. This was no anomaly; these numbers are very consistent from election to election. We could show you the same chart for pretty much any of the last six or seven elections, and it would look about the same.

It is possible - and, in fact, desirable - to take advantage of this property when building a forecast model.

For instance, my analysis has found that when polls in a state are out of line with its relative popular vote from the past election or two, it often snaps back into place by November, unless this pattern is explained by another factor like the state's being the home of one of the candidates. This is why our forecast model gives quite a bit of weight to what I call “state fundamentals,” the largest of which is simply how the state has voted recently.

You might call this the “top-down” method. Figure out th e national trend, then back into an estimate of where the vote should be in each state based upon that.

Say, for example, that Washington state typically votes about 10 points more Democratic than the country as a whole. If Mr. Obama leads by two points nationally, that would imply that he would win in Washington by about 12 points.

But can't this also work the other way around? Say you have a poll showing Mr. Obama ahead by 12 points in Washington, and you know that Washington is 10 points more Democratic than the national average.

Can't you infer from that poll that Mr. Obama is ahead by about two points nationally?

This “bottom-up” approach is also informative, it turns out. Or to put it another way, a poll in one state tells us something about the conditions of the race in the other 49 states.

Of course, this method needs to be applied quite carefully. Inferring the national trend from the polls in just one state will introduce a lot of noise into the system.

But if you look at the state polls in all 50 states - or at least all states where there is a significant amount of polling - and do so in a systematic way, it can tell you quite a bit about where the national race stands. In fact, as we'll discuss in the follow-up column, the “bottom-up” method will sometimes give you a better estimate of the national popular vote than you'll get from the national polls themselves.

Let me give you a more detailed sense for how this works. First, we'll apply a relatively simple version of this calculation, then I'll give you the exact method that the FiveThirtyEight model uses.

For the simple method, we'll look at the 25 states that have been polled at least twice since May 1. Since then, the national race has been fairly stable, at least in our estimation.

In each of these states, I'm listing what I call the FiveThirtyEight modified polling average. The modified polling average starts out w ith our regular polling average, which weights the polls based on how recently they were conducted, the reliability of the pollster and the sample size of the poll. Then it makes three other adjustments: a likely voter adjustment (which reflects how polls of registered rather than likely voters typically underestimate the standing of the Republican candidate), a trendline adjustment (which reflects changes in the overall standing between the two candidates since the poll was conducted) and a “house effects” adjustment (which corrects for systematic biases toward either the Democratic or Republican candidates among certain pollsters). We've explained how each of these adjustments function in the past so I won't dwell on them now.

We can then compare the modified polling average with the relative popular vote of the state in 2008.

In New York, for example, the modified polling average put Mr. Obama 23.3 points ahead as of Tuesday's forecast. In 2008, New York w as 19.6 points more Democratic than the country as a whole.

By subtracting 19.6 points from 23.3 points, we get what I call an implied national popular vote. In this case, the result is Obama plus 3.7 points. In other words, the New York polls are most consistent with a race in which Mr. Obama leads by 3.7 points nationally.

This calculation varies some from state to state. The implied national popular vote derived from the polls in Arizona is Obama plus 8.7 points. (In this case, the high figure results in part from the fact that Arizona was John McCain's home state, meaning that it is easier for Mr. Obama to make up ground relative to the 2008 finish.) Whereas in Oregon - which Mr. Obama won easily in 2008 but where polls have shown a relatively tight race this year - the implied national popular vote is Romney plus 4.2 points.

These idiosyncratic cases tend to even out if we perform this calculation across all the states. Furthermore, we can weight the s tates based on their turnout in 2008: a deviation in the vote in Rhode Island or Wyoming will matter much less than one in California, Texas or Florida in terms of the national popular vote.

If we perform this calculation across all the states with a significant amount of recent polling, we come to a result of Obama plus 2.9 points. In other words, the totality of state polling - dozens and dozens of state polls, looked at in a careful way - is most consistent with a race in which Mr. Obama leads Mr. Romney by about three points nationally, according to this approach.

The method that our forecast model uses is similar to this, but it introduces some more nuances into the calculation.

First, instead of just looking at a state's relative popular vote in 2008, I calculate something called the FiveThirtyEight Presidential Voting Index. (The name is a takeoff on Cook Political's partisan voting index, which makes a similar calculation.)

The FiveThirtyEight Presidential Voting Index differs from the simple method in a few important ways:

It looks at the relative popular vote in both 2008 and 2004, giving the more recent year three-quarters of the weight. (My research suggests that this weighting is roughly optimal based on the historical data.)

It accounts for the “elasticity” of a state, which is the tendency of some states (like New Hampshire) to move more relative to the national trend than others.

It adjusts for home state effects. On average, a presidential candidate gets a seven-point push in his home state, and a two-point push in the home state of his vice-presidential nominee. We subtract these numbers when looking at the performance of the states in 2004 and 2008. (For instance, the method accounts for the fact that some of Mr. McCain's strong performance in Arizona in 2008 was because it was his home state.) Then, we add the numbers back in for the home states of the candidates in 2012. (Mr. Romney is expected to do better in his home state of Massachusetts than a Republican typically would.)

Finally, we make sure that the index is properly calibrated, such that the average voting index across all 50 states and the District of Columbia is exactly zero, weighted by turnout. (Turnout estimates are adjusted for population growth in the states over the past four years and for changes in voter identification laws, although neither of these adjustments makes very much difference.)

Although this calculation might seem involved, the way to read the voting index is relatively straightforward. In Missouri, for example, the index is Republican plus 6.7 points. What this means is that if the popular vote were exactly tied nationally, we'd expect the Republican candidate to carry Missouri by 6.7 percentage points.

We can use this index to calculate an implied national popular vote, just as we did with the simpler method before.

There are two more wrinkles that the FiveThirtyEight method applies. (Neither is that important, but I'm trying to document the method as completely as possible.) First, it weights each state not just based on the turnout there, but also on the quality and quantity of polling. So - although technically it determines an implied national popular vote for South Carolina - the South Carolina value receives very little weight in the overall calculation since the only poll there was conducted months ago. Second, it adjusts the difference between a state's modified polling average and its voting index by its elasticity score, which reflects the fact that some states are “swingier” than others, making it easier to make gains at the margin there.

Based on the official version of the calculation, the implied national popular vote from the state polls is Obama by 3.6 points.

In plain English, if you had to guess what the national popular vote was from the state polls alone - without ever looking at a national poll - the best estimate would be that Mr. Obama was ahead in the race by three or four points, even after adjusting for likely voters and for other factors.

This is slightly larger than the lead suggested by national polls alone, which put Mr. Obama ahead by about one or two points instead, according to our method.

In other words, there is some divergence between the “top-down” and “bottom-up” approaches - the totality of state polls implying a somewhat more favorable result for Mr. Obama than the national polls do. Our “fancy” way of looking at the numbers doesn't resolve the dilemma that I introduced earlier on.

In Wednesday's column, we'll explore different hypotheses that might explain these differences, and consider the best policy when they arise.

This post has been revised to reflect the following correction:

Correction: July 25, 2012

Two charts accompanying an earlier version of this post showed President Obama ahead in the polling average of Montana. He is behind in the state, not ahead.