Nebraska G.O.P. Draws a Tougher Map for Obama

September 23, 2012, 8:06 am

By MICAH COHEN

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. Here is a look at Nebraska, the Cornhusker State. FiveThirtyEight spoke with John R. Hibbing, a professor of political science at the University of Nebraska-Lincoln, and Paul Landow, a professor of political science at the University of Nebraska at Omaha.

The most impressive victory of President Obama's 2008 campaign may have also been the most minute: he won a single electoral vote by a single percentage point in Nebraska's Second Congressional District. (Nebraska is one of two states, along with Maine, that awards electoral votes by Congressi onal district.)

Nebraska's Second District was the reddest area Mr. Obama carried in 2008. It falls to the right of traditionally Republican states like North Carolina and Virginia on FiveThirtyEight's Presidential Voting Index and was the farthest Mr. Obama was able to penetrate into G.O.P. territory.

But after the election, Nebraska Republicans responded with a fairly simple strategy. They moved the Second District even farther behind the battlements, redrawing the district lines after the 2010 Census to make it more Republican and “avoid what they considered to be the debacle of losing the seat to Obama in 2008,” Mr. Landow said.

The Second District's new boundaries make it more likely that all five of Nebraska's electoral votes will go to Mitt Romney this year. As a whole, Nebraska is among the most conservative states. In the last half-century, only Utah has favored G.O.P. presidential candidates by consistently wider margins.

Nebraska is rural, mostly white and fiscally and socially conservative. It is similar both geographically and ideologically to its southern neighbor, Kansas. Western Nebraska, the Third Congressional District, is almost uniformly Republican. It is sparsely populated, with vast empty expanses broken by the occasional ranch or rail yard.

The eastern fifth of Nebraska, the First and Second districts, are more developed. More consistent rainfall allows for better farming. But the region is still lightly populated and heavily Republican. In presidential elections, Democrats are competitive in just a few areas: Lancaster County, which includes the state capital, Lincoln, and the main campus of the University of Nebraska; Thurston County, which is majority Native American but has only several thousand residents; and the Second District, anchored by Omaha.

Before the latest round of redistricting, the Second District included Omaha's Douglas County and the eastern half of Sarpy County. The western half of Sarpy was part of the First District.

The geography is important. Both Douglas and Sarpy counties are more Democratic-leaning in the east, Mr. Landow said, transitioning from urban and suburban to exurban and rural as you travel from east to west. So when Nebraska Republicans redrew the district lines, they flipped Sarpy County around, moving the western half into the Second District and the eastern half into the First District. The First District is more Republican than the Second District, so it could safely absorb some Democratic voters.

“A lot of working-class Democrats in eastern Sarpy County were taken out of the Second District,” Mr. Landow said.

(To see how the districts changed, go to Govtrack.us, which has a useful map where you can toggle back and forth between the old and new boundaries. See here).

Omaha's Democratic constituencies are substantial but not overwhelming. Douglas County is 12 percent black and 12 percent Hispanic. One of the main industries in the area is food processing, including meatpacking, which employs blue-collar, Democratic-leaning voters, Mr. Landow said.

But Omaha is also home to white-collar, more Republican-leaning industries; the city is a regional center for financial services, insurance and banking. And overall, the Second District was Republican-leaning in 2008, and is even more so in 2012.

“It's the closest thing we have to a competitive region of the state,” Mr. Hibbing said, “but I still wouldn't classify it as quite competitive because it is really hard for Democrats to do well there.”

The Bellwether: Dodge County

Dodge County, to the northwest of Omaha, has come within a couple percentage points of the statewide vote in the last three presidential elections. It is mostly rural and mostly Republican, like Nebraska as a whole. But Dodge County also includes a decent-sized town, Fremont, whi ch has a small but growing university, Mr. Hibbing said.

The Bottom Line

Mr. Romney is a 100 percent favorite to carry four of Nebraska's five electoral votes, according to the current FiveThirtyEight forecast. He should win the two statewide votes as well as the votes awarded to the winner of the First and Third congressional districts.

Republicans are likely to maintain their advantage in the Cornhusker State for the foreseeable future. Like Kansas, Nebraska has been moving to the ideological right over the last two decades. In addition, the state's economy is in excellent shape, and its population is mostly stable, Mr. Hibbing said.

The only demographic change with the potential to help Democrats is an influx of Latinos, who have moved to Nebraska for jobs in agriculture and food processing. In 1990, the state's Hispanic population was just 2 percent. Today, it is almost 10 percent. But, as in Kansas, the Latino population in Nebraska has yet to ma ke an impact politically.

Mr. Obama is facing more headwinds in 2012 than he was in 2008 and would likely have had difficulty retaining Nebraska's Second District even if it had not been redrawn. He carried it by just 3,370 votes in 2008.

In its new, more Republican-leaning shape, the Second District is an even tougher place for Mr. Obama to repeat his 2008 success. Mr. Romney is a 94 percent favorite there, according to the current forecast.

Sept. 22: Little Agreement Among Pollsters on \'Enthusiasm Gap\'

September 22, 2012, 7:41 pm

By NATE SILVER

Saturday brought a light volume of polling data, and the FiveThirtyEight forecast was not much changed. Barack Obama's chances of winning the Electoral College are 77.5 percent, according to the model, slightly improved from 76.9 percent in Friday's forecast.

The polls that were published since our Friday update, all of which were national polls, had mixed results. Mr. Obama gained ground on Mitt Romney in the online tracking polls conducted by Ipsos and by the RAND Corporation. Nevertheless, he lost two percentage points in the Rasmussen Reports tracking poll, and his numbers held steady in the Gallup tracking poll, which continues to show a tied race. (We'll have more about how to think about that Gallu p poll in a separate article.)

Mr. Obama's numbers also held steady, at a four-point lead among likely voters, in a United Press International national poll, which is being published roughly once per week.

Over all, Saturday's data seemed like a total wash - so why did Mr. Obama's forecast improve, even incrementally?

The reason is that we are now getting to the point where a neutral day in the polls can be thought as being ever-so-slightly favorable to Mr. Obama, since he leads in the race and since Mr. Romney now has only 45 days to make up the deficit. This will be especially true over the course of the next week or so, during which time the penalty that the model has been applying to Mr. Obama's polls because of the potential aftereffects of the Democratic convention will phase out.

Another way to look at this: Mr. Obama's win probability in our “now-cast,” which is our estimate of what would happen if the election were held today, is 95.8 percent. (The “now-cast” also does not apply the convention bounce penalty to Mr. Obama's polls.) As Election Day draws nearer, the forecast will converge toward the now-cast, until eventually they are exactly the same on Nov. 6.

Still, you should generally not read very much into changes of such a small magnitude in the FiveThirtyEight forecast. The probabilities that we report are based on 25,001 simulations that we run each day. That's a lot of simulations, but it still leaves a small margin of error of about 0.5 percentage points on the daily win probability estimates.

The more significant trend is that Mr. Obama's forecast has been moving upward for several consecutive days; his current win probability of 77.5 percent is up from 72.9 percent on Tuesday.

Mixed Results Among Likely Voter Models

Unusually, the U.P.I. poll had Mr. Obama with a larger lead among likely voters than among the broader universe of registered voters, with whom he led by roughly two percentage points instead. Most polls this year have shown that Mr. Obama's numbers are worse among likely voters than among registered ones.

We diligently keep track of national and state polls that report both registered voter and likely voter numbers since they are instrumental in the likely voter adjustment that the model applies. An initial round of polls completed just after the Democratic convention suggested that the gap between the two sets of results had narrowed, although since then we've seen results that are all over the place.

An Associated Press poll earlier this week, for instance, had Mr. Obama with a 10-point lead among registered voters but just a one-point lead among likely voters, making for an enormous nine-point “enthusiasm gap” in favor of Mr. Romney. But then there are scattered cases, like the U.P.I. poll or last week's Fox News national survey, in which Mr. Obama actually did better in the lik ely voter version of the poll.

Likely voter models are a necessary evil - and polls will normally overstate the performance of the Democratic candidate without them. But there are so many different ways to apply them - some of which are clumsily designed - that they can sometimes make the data noisier.

Still, most polling firms are clustering in the range of showing Mr. Obama performing one to four points worse among likely voters than among registered voters.

For some reason, the gap seems to be smaller in state polls - where it has averaged about 1.5 percentage points in polls published since the Democratic convention - than in national polls.

Most of the state-level polls are of swing states, and it is theoretically possible that Mr. Obama's “ground game” is having some favorable impact in these places, helping to reduce the turnout advantage that Republicans normally enjoy. If so, it is possible that Mr. Obama's position would be stronger in t he Electoral College relative to the national popular vote.

Still, because there has been so much divergence in pollsters' estimates of the enthusiasm gap, and because the mix of polling firms is somewhat different at the state and the national levels, I think we will need to see another couple of weeks' worth of data before we can come to too many conclusions about this.

For the time being, the model evaluates the Electoral College as being a fairly neutral factor this year, or perhaps even one that slightly favors Mr. Romney.

Part of the reason why is that, although Mr. Obama has had fairly strong polls since his convention in the swing states, he has also shown improvement in his polls in large-population blue states like California, New York and Massachusetts.

If Mr. Obama wins California by 25 points rather than 20, for instance, that would increase his share of the national popular vote by 0.5 percentage points. But these votes are wasted in ter ms of the Electoral College since Mr. Obama was all but certain to win California anyway.

Sept. 21: Presidential Race Changes, but Swing States Stay the Same

September 21, 2012, 10:33 pm

By NATE SILVER

We make an effort to be disciplined about the way that we characterize the polls each day. Generally speaking, if the FiveThirtyEight forecast moves appreciably toward President Obama, the tenor of the article is going to be favorable to him - and likewise for Mitt Romney, if the same is true for him.

If the forecast remains unchanged, we won't try to emphasize the smallest ticks of movement.

Sometimes, though, a day's worth of polling falls into the awkward middle ground between being a good day for one of the candidates and revealing little new information about the state of the campaign.

Friday was one such case: a reasonably strong day in the polls for Mr. Obama, but nothing that ought to alter our impressions of the race.

Mr. Obama's chances of winning the presidential election are listed at 76.9 percent by the forecast model, an incremental improvement from 76.1 percent on Thursday.

The trend over the last three days is clearer: Mr. Obama's forecast is up from a 72.9 percent chance of winning the Electoral College on Tuesday. However, he remains off his highest point in the forecast early last week, when he topped out at 80.8 percent.

Emblematic of Mr. Obama's good-but-not-great polling day were a set of polls from the firm Purple Strategies, which had him ahead in four of the five swing states: Ohio, Virginia, Colorado and North Carolina. However, Mr. Obama still trailed Mr. Romney by one point in Florida, according to the poll.

Purple Strategies had polled all of these states but North Carolina previously, and Mr. Obama's standing improved on average by three percentage points from the polls they condu cted in August.

This is consistent with the post-convention bounce that we've seen for Mr. Obama on the whole. The FiveThirtyEight “now-cast” estimates that if an election were held today, Mr. Obama would have a 95 percent chance of winning it. Additionally, he is projected to win the national popular vote by almost five points â€" up from about two points before the conventions. The three-point gain is the same as in the average Purple Strategies poll.

Our Nov. 6 forecast continues to be more conservative, however, as we still need to account for the possibility that Mr. Obama's numbers are inflated by the aftereffects of his party's convention. By this time next week, it will be safer to conclude that Mr. Obama's gains are permanent, and the forecast will move toward Mr. Obama if Mr. Romney does not make some tangible improvement.

The Purple Strategies polls, which were conducted by automated script, are also consistent with the recent data in another way. While they are decent for Mr. Obama, they are not as good for him as polls that use live interviewers and call cellphones along with landlines, which have had him ahead by about six points on average in swing states.

As the overall race has changed, however, one thing largely hasn't: the states that look as though they'll be the most important to the outcome.

The table below represents a comparison between the forecast that we ran on Aug. 28 (I chose this date because it was the last one before any polls would have been affected by the Republican convention) and the one on Friday. It shows Mr. Obama's projected margin of victory or defeat, now and then, in the 11 swing states that the campaigns and the pollsters have concentrated most of their efforts on.

Mr. Obama's projected margin of victory in the national popular vote has improved by 0.9 percentage points since Aug. 28, from 2.4 points to 3.3 points. (Note, again, that this reflects the expectati on that Mr. Obama's polls will probably recede some between now and Nov. 6; he'd be a favorite to win by more than 3.3 points in an election held today.)

In most of the swing states, Mr. Obama's forecast has improved by almost exactly that margin. His projected margin of victory in Ohio and Virginia has improved by 1.0 percentage points since that time and by 0.8 percentage points in Florida. His numbers have improved by 1.1 percentage points in Iowa and by 0.6 percent in Pennsylvania.

There are two states where Mr. Obama's forecast has actually declined: New Hampshire and North Carolina. But the decline has been modest, and might not easily be differentiated from statistical noise. New Hampshire, in particular, has not been polled as much as the other states, especially by the polls that use industry-standard methodology. It's easy enough to imagine a CNN or NBC poll coming out next week that puts Mr. Obama seven or eight points ahead there, which might be enoug h to reverse out the trend.

Mr. Obama's numbers have also been slightly weaker in Nevada and Colorado than in other swing states recently. But his outlook has still slightly improved in those states since August, and the change has probably not been enough to appreciably impact campaign strategy.

Mr. Obama has technically made his largest gains in Michigan, where his forecast improved by 1.7 percentage points, and in Wisconsin, where it has grown by 1.6 points. Still, these shifts are only slightly different from the overall national trend.

Mr. Romney, in my view, must continue to contest Wisconsin. It is ranked fourth in the country on our tipping point list, which ranks the states that are most likely to provide the decisive votes in the Electoral College in a close election.

If there's one state where the latest polls might merit a substantive change in campaign strategy, it could be Michigan. That's because Michigan was only marginally competitive before, and with the latest polls having shown strong numbers for Mr. Obama there, it now seems extremely unlikely to be a part of Mr. Romney's strongest comeback plan. The forecast estimates that Mr. Obama has a 96 percent chance of winning Michigan on Nov. 6.

A similar argument might be made about North Carolina, another state whose importance to the electoral math we have questioned in the past.

The numbers in North Carolina polls have been a bit mixed, and Mr. Obama could certainly win it. But he has little reason to bother with it when his bounce has manifested itself more clearly in most of the other swing states, and when those states sufficiently provide a myriad number of ways for him to reach 270 electoral votes.

But none of these Electoral College calculations will matter unless Mr. Romney can improve his overall standing in the race. If the national popular vote is within one or two percentage points, a split outcome is possible, but it is exce ptionally unlikely otherwise.

For the time being, instead, most of the value in swing state polls is that they provide useful information about the state of the national campaign. In general, the gains that Mr. Obama has made in the state polls have been quite consistent, both with one another and with the national trend.

The FiveThirtyEight model uses state polls alongside national ones to calculate the current trend in the race. Doing so often lends more stability to the forecast than using national polls alone.

We have added nearly 100 state polls to our database over the course of the past week. If you can't infer some useful information from those, and instead insist on calibrating your expectations of the race from one or two tracking polls, you're going to have a warped perspective on where the contest stands.

Sept. 20: Obama\'s Convention Bounce May Not Be Receding

September 21, 2012, 8:19 am

By NATE SILVER

President Obama's position inched forward in the FiveThirtyEight forecast on Thursday. His chances of winning the Electoral College are 76.1 percent, according to the forecast, up from 75.2 percent on Wednesday. Mr. Obama's projected margin of victory in the national popular vote also increased slightly, to 3.4 percentage points.

By and large, the story that Thursday's polls told was the same one as on Wednesday. Mr. Obama continues to get very strong results in state polls that use industry-standard methodology, meaning that they use live interviews and place calls to mobile phones along with landlines.

In the 10 states that have generally been ranked the highest on our tipping-point list - Ohio, V irginia, Florida, Wisconsin, Colorado, Nevada, Iowa, Pennsylvania, New Hampshire and Michigan - there have been 21 such polls since the Democratic convention ended. Mr. Obama has led in all 21 of these surveys - and usually by clear margins. On average, he has held a six-point lead in these surveys, and he has had close to 50 percent of the vote in them.

Mr. Obama's results have been more varied among polling firms that use different methodologies. A series of polls in eleven swing states, released on Thursday by the online firm YouGov, were fairly strong for Mr. Obama, putting him ahead among likely voters in all of the states except North Carolina.

But automated polls, like those from the Rasmussen Reports, have had lukewarm results for Mr. Obama. A Rasmussen Reports poll released on Thursday, for instance, put Mr. Obama three points behind in Iowa.

I don't mean to keep repeating this point about polling methodologies, b ut it really does seem to be the easiest way to unpack the state-level data right now.

In contrast to the six-point lead Mr. Obama has held on average among the swing-state polls that included cellphones, and the five-point lead he had on average among the YouGov Internet surveys, Mr. Obama has been ahead by just two points on average in polls that called landlines only, most of which were “robopolls” conducted by automated script.

If Mr. Obama's lead is five or six points in the typical swing state right now, then Mitt Romney will probably need some sort of external contingency to give him much of a chance at winning.

If Mr. Obama's lead is more like two points instead, then routine factors like the debates or economic reports could more easily put Mr. Romney ahead, although obviously there would be no guarantees.

Although the forecast model weighs polls from the stronger polling firms more heavily, it continues to project something of an in-betw een result - in part because the national polls seem to have gravitated more toward the range of a three- or four-point lead for Mr. Obama, and in part because it continues to assume that Mr. Obama could still be experiencing a modest afterglow from his convention that will subsequently fade.

However, Mr. Romney will need to see Mr. Obama's numbers decline fairly soon if he wants to bank on the convention bounce hypothesis. The penalty that the forecast is applying to Mr. Obama's polls will phase out over the next week or so. The model would make Mr. Obama a 83.9 percent favorite right now were it not for the convention bounce adjustment.

But isn't Mr. Obama's convention bounce declining already? It sure seemed to be the case a couple of days ago - but now the evidence has become more ambiguous.

The most powerful argument that Mr. Obama's convention bounce is fading - or perhaps has already faded - is the Gallup national tracking poll, which showed the race reverting to a tie on Thursday after once having given Mr. Obama a seven-point lead.

Gallup is one of four national tracking polls, however, and the others tell a variety of stories, none of which are exactly consistent.

In the Rasmussen Reports tracking poll, Mr. Obama's numbers faded sharply late last week, but they have since rebounded. In Thursday's version of that poll, he held a three-point lead over Mr. Romney when voters who leaned toward a candidate were included.

In the Ipsos online tracking poll, Mr. Obama's numbers have fluctuated some, but he remains five points ahead among likely voters - only slightly off his peak. (The survey also put Mr. Obama 10 points ahead among the broader universe of registered voters.)

In the RAND Corporation's tracking poll, Mr. Obama lead has expanded slowly but steadily. In fact, he reached his highest level of the year on Thursday, with the survey giving him a 5.4 percentage point advantage among likely vot ers.

A simple average of the four tracking polls put Mr. Obama 3.4 percentage points ahead on Thursday. That is essentially no different than a week ago, when the same technique gave him a 3.5-point lead.

It's at least possible that Mr. Obama's bounce was fading - but that the attention to Mr. Romney's ”47 percent” comments has since given Mr. Obama renewed momentum. It will take a few more days before we can come to any sort of conclusion about this, however, especially since some of the tracking polls use long field periods and have only conducted a fraction of their interviews since Mr. Romney's remarks were uncovered.

It's also possible that we've been jumping the gun. The four national tracking polls all shot up very quickly after the Democratic National Convention, to the point that it seemed possible that Mr. Obama might eventually (if temporarily) gain as much as a six- to eight-point advantage in the race.

But the Gallup tracking poll, wh ich showed an especially sharp shift, could have been exaggerating it because of statistical variance - and now may be underselling it for the same reason.

Last week, Mr. Obama's state polls seemed to be underwhelming relative to his national ones. This week, just the opposite has been true. That might lend credibility to the hypothesis that the some of the national trackers initially exaggerated the extent of Mr. Obama's bounce - but also, that the Gallup poll now exaggerates his decline.

Of course, if you're a purist, then the Gallup survey is the only one of the four tracking polls that you'll find acceptable, since it's the only one to use a traditional methodology. But then you have to reconcile that with the fact that the polls using the strongest methodological standards at the state level are now giving Mr. Obama a six-point lead in the battleground states.

Mr. Romney would much prefer the robopolls, warts and all. And if his numbers don't improve s oon, he had better hope that they are right.

Sept. 20: Obama\'s Convention Bounce May Not Be Receding

September 21, 2012, 8:19 am

By NATE SILVER

President Obama's position inched forward in the FiveThirtyEight forecast on Thursday. His chances of winning the Electoral College are 76.1 percent, according to the forecast, up from 75.2 percent on Wednesday. Mr. Obama's projected margin of victory in the national popular vote also increased slightly, to 3.4 percentage points.

By and large, the story that Thursday's polls told was the same one as on Wednesday. Mr. Obama continues to get very strong results in state polls that use industry-standard methodology, meaning that they use live interviews and place calls to mobile phones along with landlines.

In the 10 states that have generally been ranked the highest on our tipping-point list - Ohio, V irginia, Florida, Wisconsin, Colorado, Nevada, Iowa, Pennsylvania, New Hampshire and Michigan - there have been 21 such polls since the Democratic convention ended. Mr. Obama has led in all 21 of these surveys - and usually by clear margins. On average, he has held a six-point lead in these surveys, and he has had close to 50 percent of the vote in them.

Mr. Obama's results have been more varied among polling firms that use different methodologies. A series of polls in eleven swing states, released on Thursday by the online firm YouGov, were fairly strong for Mr. Obama, putting him ahead among likely voters in all of the states except North Carolina.

But automated polls, like those from the Rasmussen Reports, have had lukewarm results for Mr. Obama. A Rasmussen Reports poll released on Thursday, for instance, put Mr. Obama three points behind in Iowa.

I don't mean to keep repeating this point about polling methodologies, b ut it really does seem to be the easiest way to unpack the state-level data right now.

In contrast to the six-point lead Mr. Obama has held on average among the swing-state polls that included cellphones, and the five-point lead he had on average among the YouGov Internet surveys, Mr. Obama has been ahead by just two points on average in polls that called landlines only, most of which were “robopolls” conducted by automated script.

If Mr. Obama's lead is five or six points in the typical swing state right now, then Mitt Romney will probably need some sort of external contingency to give him much of a chance at winning.

If Mr. Obama's lead is more like two points instead, then routine factors like the debates or economic reports could more easily put Mr. Romney ahead, although obviously there would be no guarantees.

Although the forecast model weighs polls from the stronger polling firms more heavily, it continues to project something of an in-betw een result - in part because the national polls seem to have gravitated more toward the range of a three- or four-point lead for Mr. Obama, and in part because it continues to assume that Mr. Obama could still be experiencing a modest afterglow from his convention that will subsequently fade.

However, Mr. Romney will need to see Mr. Obama's numbers decline fairly soon if he wants to bank on the convention bounce hypothesis. The penalty that the forecast is applying to Mr. Obama's polls will phase out over the next week or so. The model would make Mr. Obama a 83.9 percent favorite right now were it not for the convention bounce adjustment.

But isn't Mr. Obama's convention bounce declining already? It sure seemed to be the case a couple of days ago - but now the evidence has become more ambiguous.

The most powerful argument that Mr. Obama's convention bounce is fading - or perhaps has already faded - is the Gallup national tracking poll, which showed the race reverting to a tie on Thursday after once having given Mr. Obama a seven-point lead.

Gallup is one of four national tracking polls, however, and the others tell a variety of stories, none of which are exactly consistent.

In the Rasmussen Reports tracking poll, Mr. Obama's numbers faded sharply late last week, but they have since rebounded. In Thursday's version of that poll, he held a three-point lead over Mr. Romney when voters who leaned toward a candidate were included.

In the Ipsos online tracking poll, Mr. Obama's numbers have fluctuated some, but he remains five points ahead among likely voters - only slightly off his peak. (The survey also put Mr. Obama 10 points ahead among the broader universe of registered voters.)

In the RAND Corporation's tracking poll, Mr. Obama lead has expanded slowly but steadily. In fact, he reached his highest level of the year on Thursday, with the survey giving him a 5.4 percentage point advantage among likely vot ers.

A simple average of the four tracking polls put Mr. Obama 3.4 percentage points ahead on Thursday. That is essentially no different than a week ago, when the same technique gave him a 3.5-point lead.

It's at least possible that Mr. Obama's bounce was fading - but that the attention to Mr. Romney's ”47 percent” comments has since given Mr. Obama renewed momentum. It will take a few more days before we can come to any sort of conclusion about this, however, especially since some of the tracking polls use long field periods and have only conducted a fraction of their interviews since Mr. Romney's remarks were uncovered.

It's also possible that we've been jumping the gun. The four national tracking polls all shot up very quickly after the Democratic National Convention, to the point that it seemed possible that Mr. Obama might eventually (if temporarily) gain as much as a six- to eight-point advantage in the race.

But the Gallup tracking poll, wh ich showed an especially sharp shift, could have been exaggerating it because of statistical variance - and now may be underselling it for the same reason.

Last week, Mr. Obama's state polls seemed to be underwhelming relative to his national ones. This week, just the opposite has been true. That might lend credibility to the hypothesis that the some of the national trackers initially exaggerated the extent of Mr. Obama's bounce - but also, that the Gallup poll now exaggerates his decline.

Of course, if you're a purist, then the Gallup survey is the only one of the four tracking polls that you'll find acceptable, since it's the only one to use a traditional methodology. But then you have to reconcile that with the fact that the polls using the strongest methodological standards at the state level are now giving Mr. Obama a six-point lead in the battleground states.

Mr. Romney would much prefer the robopolls, warts and all. And if his numbers don't improve s oon, he had better hope that they are right.

Sept. 19: A Wild Day in the Polls, but Obama Ends Up Ahead

September 20, 2012, 8:24 am

By NATE SILVER

At about 1:30 on Wednesday afternoon, I tweeted in exasperation: “The. Polls. Have. Stopped. Making. Any. Sense.”

I'd just seen a Marquette University poll of Wisconsin, which put President Obama 14 points ahead of Mitt Romney there. This came after a Rasmussen Reports poll of New Hampshire, published earlier that day, which had given Mitt Romney a three-point lead in the Granite State.

There is no plausible universe in which Mr. Obama wins Wisconsin by 14 points but loses New Hampshire by three. It's not even obvious which of the states is more favorable for him. Earlier this week, for instance, we'd seen a Wisconsin poll putting Mr. Obama up just one point there, while a different survey of N ew Hampshire gave him a five-point lead.

Following the polls on Wednesday reminded me of the aphorism: “If you don't like the weather in Chicago, wait five minutes.” When there are twenty or more polls published in day, as there were on Wednesday, there are necessarily going to be some stronger or weaker ones for either candidate.

There are also going to be some outliers - sometimes because of unavoidable statistical variance, sometimes because the polling company has a partisan bias, sometimes because it just doesn't know what it's doing. (And sometimes: because of all of the above.)

By the end of Wednesday, however, it was clear that the preponderance of the evidence favored Mr. Obama. He got strong polls in Ohio, Florida, Michigan, Wisconsin and Virginia, all from credible pollsters. Mr. Obama, who had been slipping in our forecast recently, rebounded to a 75.2 percent chance of winning the Electoral College, up fro m 72.9 percent on Tuesday.

The most unambiguously bearish sign for Mr. Romney are the poor polls he has been getting in swing states from pollsters that use a thorough methodology and include cellphones in their samples.

There have been 16 such polls published in the top 10 tipping point states since the Democratic convention ended, all conducted among likely voters. Mr. Obama has held the lead in all 16 of these polls. With the exception of two polls in Colorado - where Mr. Obama's polling has been quite middling recently - all put him ahead by at least four points. On average, he led by 5.8 percentage points between these 16 surveys.

If this is what the post-convention landscape looks like, then Mr. Romney is in a great deal of trouble. Perhaps these polls imply that Mr. Obama's lead is somewhere in the range of five percentage points in the popular vote - national polls suggest that it's a bit less than that, but state polls provide useful information ab out the national landscape. Or perhaps they imply that Mr. Obama is overperforming slightly in the swing states.

Either way, that's a pretty big deficit for Mr. Romney to overcome. What's more, Mr. Obama was at 49.4 percent of the vote on average between these 16 surveys, meaning that he'd need to capture only a tiny sliver of the undecided vote to get to an outright majority. (If we're being technical, 49.4 percent might be sufficient for him to win these states on its own, since perhaps 1 or 2 percent of the vote will go to third-party candidates.)

To be clear: I do not recommend that this is the only data you look at. The forecast model also evaluates polls that exclude cellphones, although it gives them slightly less weight. Those have not necessarily shown a great deal of strength for Mr. Obama.

And just as the model looks at state polls to infer the national trend, it also does the reverse, using the national polls (and essentially the assumption of ”uniform swing”) to infer where the states stand. The national polls show a spread right now from an effective tie to an eight-point lead for Mr. Obama. Taken as a whole, they seem to imply more like a three or four point lead for Mr. Obama rather than something in the range of five points. (These distinctions really do make a difference, especially with so few undecided voters left.)

The other questions, of course, are whether Mr. Obama's bounce is fading, and if it might fade further. His FiveThirtyEight forecast remains off its high of about an 80 percent chance of victory, that he achieved late last week.

The most compelling case that Mr. Obama's bounce is diminishing is from the Gallup and Rasmussen Reports tracking polls, both of which were unchanged on Wednesday, but which have reverted sharply from their post-convention peaks and are now at their preconvention levels instead.

These tracking polls have a fair amount of influence on the FiveThirty Eight forecast at potential turning points in the race, and they are certainly worth your trouble to look at - especially the Gallup poll, which has a large sample size and uses a thorough methodology.

But just as a thought experiment: if you exclude the Gallup and Rasmussen Reports tracking polls, it isn't clear at all that Mr. Obama's bounce is decaying. His bounce in the RAND Corporation's online tracking poll has actually grown slightly, and his standing has roughly held steady (although with some fluctuations) in another online survey, from Ipsos.

The state polls allow for fewer direct comparisons, since most of them take the temperature of a state at most once every few weeks. But if anything, Mr. Obama's state polls so far this week have been a bit stronger than last week, when they were a little underwhelming.

In the FiveThirtyEight “now-cast”, which does not adjust for the effects of the party conventions as our Nov. 6 forecast does, and which considers the possibility that a candidate would win a “snap” election held today, Mr. Obama's chances rose to 94.4 percent on Wednesday, his highest position to date.

Our Nov. 6 forecast, however, continues to assume that Mr. Obama's position may be slightly inflated by his convention. Between that possibility, Mr. Obama's mediocre results in polls that do not call cellphone numbers, and the Gallup and Rasmussen trackers, the totality of the evidence continues to require some equivocation.

It's certainly possible that the story told by the high-quality swing state polls is right, but if so, we should see the consensus of the evidence (if not every last outlying or dubious poll) come into line with it soon enough. The FiveThirtyEight forecast, which makes Mr. Obama about a 3-to-1 favorite, is consistent with the odds offered at betting markets and by bookmakers. I wouldn't feel as though there were much value in placing a bet on either side of that line.

But if Mr. Obama is having days like this in the polls a week from now, then Mr. Romney is either going to be banking on an exceptionally lopsided turnout, or some sort of October surprise. Either is a possibility, but not one you'd want to put a lot of money on.

Senate Forecast: What Has Gone Wrong for G.O.P. Candidates?

September 20, 2012, 12:02 am

By NATE SILVER

The trend in the presidential race has been difficult to discern lately. President Obama has very probably gained ground since the conventions, but it's hard to say exactly how much, and how quickly his bounce is eroding.

There are no such ambiguities in the race for control of the Senate, however. Polls show key races shifting decisively toward the Democrats, with the Republican position deteriorating almost by the day.

Since we published our initial Senate forecast on Tuesday, Republicans have seen an additional decline in their standing in two major races.

Two polls of Virginia published on Wednesday gave the Democrat, the former Gov. Tim Kaine, leads of 4 and 7 percentage points over the Republican, the former Senator George Allen. The FiveThirtyEight forecast model now gives Mr. Kaine roughly a 75 percent chance of winning the seat on the strength of the new polls, up from about 60 percent in Tuesday's forecast.

The other problematic state for Republicans is Wisconsin, where their candidate, the former Gov. Tommy Thompson, had once appeared to hold the advantage.

Mr. Thompson's Democratic opponent, Representative Tammy Baldwin, had published an internal poll earlier this week showing her pulling into the lead. The FiveThirtyEight Senate and presidential forecasts do not use internal polls released directly by the campaigns, as they typically exaggerate their candidate's standing.

However, in this case, public polls have now confirmed that the race seems to have shifted. A poll by The New York Times, CBS News and Quinnipiac University showed Mrs. Baldwin having drawn into a tie with Mr. Thompson, after trai ling him by 6 percentage points last month.

A Marquette University poll, also published on Wednesday, showed a much sharper reversal, with Mrs. Baldwin going from a 9-point deficit to a 9-point lead. The Marquette poll appears to be a bit of an outlier - it also had Mr. Obama leading in the presidential race in Wisconsin by a 14-point margin, a somewhat implausible figure. Nonetheless, the model now has Mrs. Baldwin as the slight favorite, with about a 60 percent chance of winning.

It would be only a modest exaggeration to say that it's been hard to find any strong Senate polls for Republicans in the past two or three weeks. Wednesday also brought bad news for Republicans in Massachusetts, where a fourth consecutive poll showed the Democrat Elizabeth Warren ahead of Senator Scott Brown; in Connecticut, where a poll gave the Democrat Chris Murphy a slight advantage over their candidate, Linda McMahon; and in Florida, where a Fox News poll gave the Democratic incum bent Bill Nelson a 14-point lead.

One exception has been in Maine, where two new polls on Wednesday showed a deterioration in the standing of the independent Angus King, who would probably caucus with the Democrats, at the expense of both the Republican, Secretary of State Charles Summers, and the Democrat, State Senator Cynthia Dill. The model now gives Mr. King an 84 percent chance of winning, Mr. Summers 11 percent, and Mrs. Dill 5 percent.

But this is small compensation for the decline over the past two weeks of the Republicans' position in Virginia, Massachusetts, Wisconsin, Florida and Ohio, all of which have broken sharply to the Democrats.

The Democrats' chances of controlling the Senate have increased to 79 percent in the forecast, up from 70 percent on Tuesday.

Had we run the model a month ago, based on polls through Aug. 19, the Democrats' chances of maintaining Senate control would have been listed at just 39 percent.

The velocity of the change is unusual. Although Senate races in different parts of the country can sometimes move in the same direction, there was never quite this rapid a shift in our Senate forecasts in 2008 or 2010.

The forecast model is not doing anything particularly fancy; it's just that an overwhelming number of Senate polls recently have shown the Democratic candidates' standing improving.

Republicans could also have some reason to be concerned about Nevada, which has not been polled recently but where their candidate, the appointed Senator Dean Heller, maintains a slight advantage over the Democratic Representative Shelley Berkeley. Mr. Heller is a fairly strong candidate, but if there is some sort of national tide against Republicans, he could become the underdog in that race as well.

There's one comforting thought for Republicans, however. It's plausible that at least some of the Democrats' gains reflect a boost from their convention, which could wear off. I ha ve not studied whether conventions produce bounces in Congressional races and the model makes no assumptions about it, but it is a reasonable hypothesis.

However, at least some of the shift appeared to predate the conventions. The model would have had Democrats' chances of retaining the Senate improving to 50 percent from 39 percent over the course of the week beginning Aug. 19, before the Republican convention started.

I can think of two major theories to explain why the shift is occurring, one focused on Mitt Romney, and another on the overall positioning of the Republican brand.

Theory No. 1: Is Romney a Downballot Drag?

Polls show that Mr. Romney has middling personal favorability ratings but that many voters will choose him anyway because of the deteriorating economy.

Senate races, however, are less dictated by national economic conditions. Instead, they often turn more on the strengths and weaknesses of the individual candidates, and then by their stances on fiscal and social policy.

Mr. Romney has not dictated much in the way of detailed programs in these areas, and some of the policy stances that he has articulated are unpopular.

Mr. Romney has also been less able to campaign effectively against an unpopular Democratic initiative, the Democrats' health care bill, because he passed a similar bill as governor of Massachusetts.

Finally, some voters who disapprove of Mr. Obama, but who also have lukewarm feelings toward Mr. Romney, might lean toward voting Democrat for Senate in effort to ensure divided government, especially since Republicans also have control of the House.

Theory No. 2: G.O.P. Conservatism Is Hurting

An alternative hypothesis is that the shift has to do with overall perceptions of the Republican platform.

Our research has shown that statistical measures of candidate ideology are a reasonably powerful predictor of the outcome of Senate races, with candidates who are rated as holding “extreme” views performing poorly.

But in practice, ideology is in large part perceptual for voters, and may depend on which issues seem most salient at any given time.

August, at which point the shift toward Democrats in Senate races appeared to begin, was dominated by two major news items: Mr. Romney's selection of Representative Paul D. Ryan as his running mate, who has very conservative views on fiscal policy, and by the comments about rape made by the Republican Senate candidate in Missouri, Todd Akin, which may have reinforced the idea that Republicans hold very conservative positions on social issues.

These factors may have made it harder for Republicans to position themselves toward the ideological center. And in several states, including Missouri, Indiana, Michigan and Ohio, Republicans nominated sub-optimally conservative candidates.

More moderate Republican candidates, like Mr. Brown of Massachusetts and Mrs. M cMahon of Connecticut, have increasingly sought to distance themselves from the national Republican brand, and sometimes also from the Republican presidential ticket.

Some of these theories are speculative, to be sure. A large number of Senate races remain in play: of the several states in which there has been a shift against Republicans in the polls in recent weeks, perhaps only Florida seems completely lost.

But if the trend continues, the question may no longer be whether Republicans can win the Senate - but how vulnerable they are to losing the House.