Nov. 5: Late Poll Gains for Obama Leave Romney With Longer Odds

Mitt Romney has always had difficulty drawing a winning Electoral College hand. Even during his best period of polling, in the week or two after the first presidential debate in Denver, he never quite pulled ahead in the polling averages in Ohio and other states that would allow him to secure 270 electoral votes.

But the most recent set of polls suggest another problem for Mr. Romney, whose momentum in the polls stalled out in mid-October. Instead, it is President Obama who is making gains.

Among 12 national polls published on Monday, Mr. Obama led by an average of 1.6 percentage points. Perhaps more important is the trend in the surveys. On average, Mr. Obama gained 1.5 percentage points from the prior edition of the same polls, improving his standing in nine of the surveys while losing ground in just one.

Because these surveys had large sample sizes, the trend is both statistically and practically meaningful. Whether because of Hurricane Sandy, the relatively good economic news of late, or other factors, Mr. Obama appears to have gained ground in the closing days of the race.

The national polls now range from showing a 1-point lead for Mr. Romney to slightly more than a 4-point advantage for Mr. Obama. The FiveThirtyEight forecast of the national popular vote is within this range, projecting Mr. Obama's most likely margin of victory to be two or three percentage points, approximating the margin that George W. Bush achieved in defeating John Kerry in 2004.

Averaging polls together increases their sample size - making them much more powerful statistically than any one poll taken alone. But the errors in the polls are sometimes correlated, meaning there are years when most of them miss in the same direction. Mr. Romn ey remains close enough to Mr. Obama that he could fairly easily win the popular vote if there is such an error in Mr. Obama's favor this year.

Mr. Romney's chances are less, however, of winning the Electoral College. The large majority of polls in battleground states over the past three days have shown leads for Mr. Obama. On Monday, for example, 19 battleground state polls found leads for Mr. Obama, as compared with just three for Mr. Romney.

Ohio remains the largest problem for Mr. Romney, where he has been behind in most polls all year. Mr. Romney might ordinarily take some solace in the fact that Ohio is slightly Republican-leaning, but the auto bailout may have changed its character this year, as there is evidence that Mr. Obama is performing more strongly with working-class voters in Ohio than he is elsewhere in the country.

Mr. Obama could secure the Electoral College by winning Wisconsin, Nevada and Pennsylvania, along with Ohio.

A win for Mr. Romney in Wisconsin would now qualify as a substantial upset. He has not led in a poll there since August, and an increasing number of surveys there instead show Mr. Obama five or more points ahead.

Mr. Obama's margins have been narrower in Nevada, but Mr. Romney has a different type of problem there: perhaps 70 percent of the state has already voted, and Democrats have locked in roughly a 7-point advantage over Republicans from the vote so far. This margin is down for Democrats from 2008, but Mr. Romney would nevertheless need an exceptional turnout on Tuesday to make up enough ground.

This has led Mr. Romney to make a last-minute play for Pennsylvania, and there is some evidence that the state has tightened slightly. But the gains for Mr. Romney may be too little and too late, or they may have been counteracted by a national trend toward Mr. Obama. With the exception of one Republican polling firm, public polls of the state still have Mr. Obama leading by three to nine percentage points.

Moreover, Mr. Obama has a number of backup options were he to lose one or more of these states. In Iowa, Mr. Obama leads by about three percentage points in the average of polls, and by a similar margin in New Hampshire. Recent polls also suggest movement toward Mr. Obama in Colorado and Virginia, and he now appears to be favored in each one.

Florida remains too close to call. The FiveThirtyEight forecast has the race there within two-tenths of a percentage point, which would be close enough to trigger an automatic recount.

Only in North Carolina, among the battleground states, has Mr. Romney had a reasonably consistent polling edge over the final week of the campaign.

If the national popular vote winds up roughly tied, inste ad of favoring Mr. Obama by two points or so, then Mr. Romney could claw back to win Florida, Colorado and Virginia, and perhaps Iowa and New Hampshire. But Mr. Obama's lead in Ohio, Wisconsin, Nevada and Pennsylvania is clear enough to withstand some underperformance in the polls, and his margins in the polling averages there have converted into a victory on election night a very high percentage of the time historically.

In order for Mr. Romney to win the Electoral College, a large number of polls, across these states and others, would have to be in error, perhaps because they overestimated Democratic turnout. It's this possibility, more than the chance of a successful hail-mary in a state like Pennsylvania, that accounts for most of Mr. Romney's remaining chances of winning the Electoral College.

There is also the chance that Mr. Obama could finish toward the higher end of the polling range in most states. If Mr. Obama has gained a point or two nationally becau se of Hurricane Sandy or other factors, then polls taken before it may underestimate his standing in the individual states as well.

The FiveThirtyEight forecast accounts for this possibility through its trendline adjustment, which is why our forecasts now are slightly more optimistic for Mr. Obama in some states than a simple average of polls. Had there been evidence of late movement toward Mr. Romney, the trendline adjustment would instead have worked in his favor.

But Mr. Romney's chances of winning the Electoral College have slipped, and are now only about 8 percent according to the forecast model - down from about 30 percent 10 days ago.

The most notable recent case of a candidate substantially beating his polls on Election Day came in 1980, when national surveys had Ronald Reagan only two or three points ahead of Jimmy Carter, and he won in a landslide instead. That year is not comparable to this one in many respects: the economy is much better now, th ere is not a major third-party candidate in the race, and Mr. Obama's approval ratings are about 50 percent rather than 35 percent for Mr. Carter. And in 1980, Mr. Reagan had late momentum following the presidential debate that year, whereas this year the momentum seems to favor Mr. Obama.

All of this leaves Mr. Romney drawing to an inside straight. I hope you'll excuse the cliche, but it's appropriate here: in poker, making an inside straight requires you to catch one of 4 cards out of 48 remaining in the deck, the chances of which are about 8 percent. Those are now about Mr. Romney's chances of winning the Electoral College, according to the FiveThirtyEight forecast

As any poker player knows, those 8 percent chances do come up once in a while. If it happens this year, then a lot of polling firms will have to re-examine their assumptions - and we will have to re-examine ours about how trustworthy the polls are. But the odds are that Mr. Obama will win another te rm.

In Ohio, Polls Show Benefit of Auto Rescue to Obama

We conclude our Presidential Geography series, a one-by-one examination of each state's political landscape and how it is changing, with Ohio, the Buckeye State. FiveThirtyEight spoke with Herb Asher and Paul A. Beck, both professors emeritus in Ohio State University's department of political science.

If the polls are correct, and President Obama wins a narrow Electoral College victory on Tuesday, the pivotal moment of the 2012 presidential race may have actually occurred in 2009. About two months after taking office, Mr. Obama set the terms of the government's rescue of General Motors and Chrysler, a move that eventually helped to resurrect the American automobile indust ry, and, in turn, bolster the economy of the king of swing states: Ohio.

Historically, Ohio has been slightly Republican-leaning relative to the nation. But this year polls suggest that Ohio is slightly Democratic-leaning. That divergence - driven by the auto rescue and the state's improved economy, local analysts said - may prove determinative. Ohio ranks first on FiveThirtyEight's tipping point index. The model estimates there is roughly a 50 percent chance that the Buckeye State's 18 electoral votes will carry the winning candidate past the 270 mark.

Ohio's historic rightward lean has been slight - about two percentage points, on average, since 1948 - but consistent. In the 16 presidential elections from 1948 through 2008, Ohio was redder than the nation in 13. It was Democratic-leaning relative to the nation only in 1964, 1972 and 2004 (and in 2004, it leaned Democratic by less than half a percentage point).

But polls show Mr. Obama leading Mitt Romney in Ohio by about three percentage points, one point better than Mr. Obama's projected national margin, according to the current FiveThirtyEight forecast. The auto rescue's impact on Ohio's political preferences, though modest, has been decisive.

“The auto rescue is popular in Ohio,” Mr. Beck said, and because the Buckeye State was only slightly Republican-leaning, a small shift appears to have tipped the state's partisan balance.

Moreover, the auto rescue and Ohio's steadily falling unemployment rate appear to have improved Mr. Obama's standing with the very demographic group that Mr. Romney might have made inroads with: white working-class voters.

“White working-class voters in Ohio have been more supportive of Obama than white working-class voters nationwide,” Mr. Beck said.

Ohio's economy has traditionally been driven by manufacturing. “Ohio led the industrial revolution 100 years ago,” Mr. Asher said, but i n the latter half of the 20th century, globalization and the outsourcing of manufacturing jobs hurt the state's economy.

Early in the 2012 presidential campaign, during the summer, the Obama campaign saturated Ohio television with advertisements highlighting Mr. Romney's “Let Detroit Go Bankrupt” op-ed article in The Times as well as linking Mr. Romney to Bain Capital and linking Bain Capital to outsourcing, Mr. Asher said. For many Ohio voters, that effort helped undermine Mr. Romney's contention that his business experience would benefit them if he reached the White House.

As a result, Mr. Beck said, many of the white working-class voters whom Mr. Romney might have appealed to now see him “as the kind of businessman who for many of them was the problem.”

Mr. Asher added, “The Obama campaign defined Mr. Romney, and that appeal gets reinforcement by the auto bailout.”

The Democratic Party's base of support in Ohio is in the northeast part of the state, a mix of African-American and blue-collar union voters in Cleveland, Canton, Akron and Youngstown. In 2008, Mr. Obama carried Ohio by just over 200,000 votes; he carried Cleveland's Cuyahoga County by almost 250,000 votes. Northeastern Ohio is also the center of the state's auto industry, in Cuyahoga and Lake Counties.

From Cleveland, Democratic support fades as you travel west along Lake Erie (though Toledo is reliably left-leaning) and southeast along Ohio's border with Pennsylvania. Democrats have also made some gains in Ohio's other major cities. Franklin County, which includes the state capital, Columbus, has trended Democratic, and Mr. Obama made gains in Dayton in 2008, as well.

In 2008, Mr. Obama also managed to flip Hamilton County, home to Cincinnati, which had long been one of the more Republican-leaning cities in the state.

Conversely, Democratic support has eroded in southeastern Ohio, which is part of Appalachia. The southeast is culturally conservative and economically depressed. Bill Clinton carried many of the counties there, but they have moved sharply toward the G.O.P. since then. Coal is a major economic driver in southeastern Ohio, and Mr. Romney has targeted voters in the area by attacking Mr. Obama's energy policies. But the southeast is also lightly populated, contributing only about 10 percent of the statewide vote, Mr. Asher said.

Outside of the northeast and Columbus, Dayton and Cincinnati, Ohio is mostly Republican-leaning. Western Ohio, in particular, is ruby red and socially conservative. To carry the state, Mr. Romney will need to run up his margins in the suburban and exurban counties in southwestern Ohio around Cincinnati as well as the small towns along the state's western border. In 2008, Senator John McCain carried those counties, but he did not get the turnout and margins that George W. Bush did in 2004.

The Bellwether: Stark County

Stark County, anchored by Canton, has been an almost perfect bellwether for the statewide vote in Ohio in the past three presidential elections. Canton tends to vote Democratic, but Stark County also has more rural areas that lean Republican. Stark County was one percentage point more Republican-leaning that Ohio over all in 2008 and 2000 and two points more Republican-leaning in 2004.

The Bottom Line

Mr. Obama is an 85 percent favorite to carry Ohio, according to the current FiveThirtyEight forecast. Not coincidentally, that almost exactly matches his odds of winning re-election, according to the model.

If not for the auto rescue, Ohio's slight Republican lean would most likely have remained in effect. Unlike in other states, there are no major demographic trends affecting the state's partisan balance.

“Ohio in terms of demographics is a fairly static state,” Mr. Beck said. “Our Hispanic population is too small to matter except at the margins.”

If Ohio were, relative to the national popular vote, two percentage points Republican-leaning this election - its average over the last 60 years - the state would be a tossup. And if Mr. Romney were able to carry Ohio, he would have many more paths to the 270 electoral votes he needs to win the White House.

But if the polls are right, and the auto rescue and Ohio's relatively healthy economy help Mr. Obama prevail in the Buckeye State , then it becomes difficult - though not impossible - for Mr. Romney to piece together a winning electoral map.

Nov. 4: Did Hurricane Sandy Blow Romney Off Course?

If President Obama wins re-election on Tuesday, the historical memory of the race might turn on the role played by Hurricane Sandy.

Already, some analysts are describing the storm as an “October surprise” that allowed Mr. Obama to regain his footing after stumbling badly in the first presidential debate and struggling to get back on course. Some Republicans seem prepared to blame a potential defeat for Mitt Romney on the storm, and the embrace of Mr. Obama by New Jersey Gov. Chris Christie and other public officials.

The theory has some appeal. The last three days of polling have brought what is almost certainly Mr. Obama's strongest run of polling since the first presidential debate in Denver. Mr. Obama led in the vast majority of battleground-state polls over the weekend. And increasingly, it is hard to find leads for Mr. Romney in national surveys - although several of them show a tie.

When the hurricane made landfall in New Jersey on Oct. 29, Mr. Obama's chances of winning re-election were 73 percent in the FiveThirtyEight forecast. Since then, his chances have risen to 86 percent, close to his highs on the year.

But, while the storm and the response to it may account for some of Mr. Obama's gains, it assuredly does not reflect the whole of the story.

Mr. Obama had already been rebounding in the polls, slowly but steadily, from his lows in early October - in contrast to a common narrative in the news media that contended, without much evidence, that Mr. Romney still had the momentum in the race.

Moreover, there are any number of alternatives to explain Mr. Obama's gains before and after the storm hi t.

Mr. Obama was adjudicated the winner of the second and third presidential debates in surveys of voters who watched them.

The past month has brought a series of encouraging economic news, including strong jobs reports in October and last Friday.

The bounce in the polls that Mr. Romney received after the Denver debate may have been destined to fade in part, as polling bounces often do following political events like national conventions.

Democrats have an edge in early voting based on states that provide hard data about which party's voters have turned out to cast ballots. Some voters who were originally rejected by the likely voter models that surveys apply may now be included if they say that they have already voted.

Both Mr. Obama and Mr. Romney have been running lots of advertisements, which could have some effect, especially in the swing states.

Mr. Obama's voter-targeting operation may in fact be stronger than Mr. Romney's and may have begun to show up in the polls.

Mr. Obama's approval rating is at 49 or 50 percent in many surveys, a threshold that would ordinarily predict a narrow re-election for an incumbent.

Some elections “break” toward one or another candidate at the end as undecided voters tune in and begin to evaluate their decision.

Each of these hypotheses could merit its own article. But the point is that the causes for Mr. Obama's gain in the polls are overdetermined, meaning that there are lot of variables that might have contributed to the one result.

If I had told you in January that Mr. Obama's approval rating would have risen close to 50 percent by November, and that the unemployment rate would have dropped below 8 percent, you likely would have inferred that Mr. Obama was a favorite for re-election, with or without a hurricane and what was judged to be a strong response to it.

This is not to dismiss the effects of the hurricane entirely. But the fact that Mr. Obama's rebound in the polls has been slow and steady, rather than sudden, would lend weight to some of these other ideas, even if they make for less dramatic narratives.

Sunday's Battleground State Polls

Although the outcome of the election is not yet known, we are at the point where the polling averages in each state are pretty much locked in - and it is mostly a question of whether the actual results will approximate them, in which case Mr. Obama should claim enough electoral votes between Ohio and other states to win another term.

Given the extremely large volume of polling data that has been published in the closing days of the campaign, you s hould mostly be looking for cases in which there are trends apparent across several different surveys of the same state.

For example, Mr. Obama led in four separate polls of Virginia on Sunday, three of which represented improvement from the prior polls issued by the same polling firms. Virginia has moved out of the tossup category into a state that leans toward Mr. Obama; he has between a 70 and a 75 percent chance of winning it, according to the forecast model.

That represents a problem for Mr. Romney because Virginia's 13 electoral votes could potentially substitute for Ohio's 18 under many electoral configurations. If Mr. Obama were to win Virginia along with Wisconsin, Nevada and either Iowa or New Hampshire, he would have enough electoral votes even if he lost Ohio.

Mr. Obama's polls in Iowa were not as strong on Sunday as they had been earlier in the week. Increasingly, it looks as though Mr. Obama's first line of defense consists of Ohio, Wisconsin and Nevada specifically, which would usually allow him to win the Electoral College on their own.

Mr. Obama's standing in Ohio seems to have drifted upward to a lead of about three points from two, reducing the risk of a polling error there.

North Carolina, where Mr. Romney led surveys on Sunday, does not appear as though it will play a central role in the electoral math.

What about that poll in Michigan, which had Mr. Romney leading by about a point?

The problem is that the polling firm, Foster McCollum White Baydoun, has had extremely Republican-leaning results (it found Mr. Romney 15 points ahead in Florida earlier this year) and shows a close race pretty much every time it polls Michigan. Other recent polls of the state do not show the same result, and the campaigns are not treating Michigan seriously as a battleground state based on their pattern of advertising expenditures and other resources.

Pennsylvania has more merit as a last-ditch ta ctical play for Mr. Romney - but it is another case where the characterization of the race as having tightened relies in part on a selective reading of the evidence. Between Saturday and Sunday, five polls of Pennsylvania had Mr. Obama an average of four points ahead there, and they did not show much of a trend, with Mr. Obama having led by the same amount on average in the previous editions of the same surveys.

State and National Polls Come Into Better Alignment

It appears that President Obama is likely to go into Election Day with a very modest lead in the average of national polls.

As of this writing, on Sunday evening, Mr. Obama led by an average of 1.3 percentage points across 12 national polls that had been published over the course of the prior 24 hours. The range was quite tight, running from a tied race in the polls issued by Rasmussen Reports, CNN and Politico, to a three-point lead in three other surveys.

This happens to be a reasonably friendly group of polls for Mr. Obama, and it's more likely than not that at least some national polls published late Sunday or on Monday will still show Mitt Romney ahead.

Nevertheless, there is enoug h data to conclude that Mr. Obama probably has a slight edge from national surveys, which until recently had pointed toward a tie - or perhaps a modest advantage for Mr. Romney in the immediate aftermath of the Denver debate.

A number of these polls had very large sample sizes, meaning that the results are less likely than usual to have resulted from statistical variance.

But the modest gains that Mr. Obama has made in the high-profile national surveys should not be that much of a surprise. We've observed the race shifting toward him over the past two to three weeks in polls of swing states, where overwhelming majorities of polls have had Mr. Obama ahead over the past few days.

Where has Mr. Obama shown a bit of weakness in his numbers? His polls in noncompetitive states have been mediocre lately. In polls published by the online firm YouGov on Sunday, for example, there were declines in Mr. Obama's numbers in California and Tex as. Since these states have large populations, they could lower Mr. Obama's popular vote even though they will play no role in his Electoral College tally.

The forecast model still does perceive some differences between the state polls and national polls, but it is within a reasonable range.

Perhaps more important, the fact that the national polls now suggest a slight lead for Mr. Obama removes one of the better reasons to think that our forecast might have been underrating Mr. Romney's chances.

Based on the simulations that we ran on early Sunday evening, for example, Mr. Obama would have an 85 percent chance of winning the Electoral College if the popular vote were exactly tied nationally. This is where Mr. Obama's Electoral College advantages, particularly in Nevada, Ohio and Wisconsin, would be of their maximum benefit. Given a tied national popular vote, we would expect Mr. Obama to underperform his polls slightly in these states - but since he leads b y a minimum of about three points in the polling average in each one, he could underperform those numbers and still win them.

Mr. Obama would be almost certain to win the Electoral College if he won the popular vote by a percentage point or so.

Instead, the model estimates that Mr. Romney would need to win the national popular vote by about one percentage point to avert a tossup, or a loss, in the Electoral College. A tied popular vote, as Mr. Romney's better national surveys now indicate, would likely yield an unhappy outcome for him.

Mr. Romney would not be in much danger of losing the Electoral College if he won the popular vote by more than about 1.5 percentage points. For example, he would be about a 95 percent favorite in the Electoral College if he won the popular vote by two percentage points, according to the forecast model.

But with national polls now showing a slight edge for Mr. Obama, these outcomes have become less likely. If Mr. Romney wins the popular vote, it may be only barely, and that might not be enough for him to win the Electoral College.

The consolidation between the national polls and state polls is also important outside the context of the FiveThirtyEight forecast model itself, since it removes a source of structural uncertainty - the chance that the model was not a good representation of the real world. While I think the model handles the relationship between state polls and national polls in a careful way, there are a lot of alternative assumptions that one might make, and so it had been a source of some inherent ambiguity.

On Saturday, we wrote that state polls would have to be statistically biased against Mr . Romney for him to win the Electoral College. Now, it may be the case that the national polls would have to be biased against him as well.

In Virginia, It\'s Tradition Versus Change

We continue our Presidential Geography series, a one-by-one examination of each state's political landscape and how it is changing. Here is Virginia, the Old Dominion. FiveThirtyEight spoke with Daniel Palazzolo, a professor of political science at the University of Richmond, and Geoffrey Skelley, a political analyst at the University of Virginia's Center for Politics.

Polling of the presidential race in Virginia has been particularly volatile. Since the beginning of October, polls at various points have shown both a seven-point lead for Mitt Romney and a seven-point lead for President Obama.

The political landscape in Virginia has shifted dramatically in recent yea rs, and the disagreement among the polls is essentially a disagreement about which Virginia will dominate on Election Day: the reliably Republican “Old Virginia,” which is more religious, rural, working-class and white, or the politically competitive “New Virginia,” which is more secular, urban, diverse and white-collar.

In 2008, New Virginia made its debut at the presidential level, with Mr. Obama becoming the first Democrat to carry the state since 1964. He won by six percentage points.

But in the following two years, Old Virginia has roared back. Turnout in nonpresidential elections tends to be substantially more favorable to Republican candidates. Bob McDonnell, a Republican, won the governor's race in 2009, and the party picked up three House seats in 2010. Republicans now represent 8 of Virginia's 11 Congressional districts.

Political analysts often group Virginia and North Carolina together as the “New South.” Both states - reliably red for years - turned blue in 2008, pushed toward the political center by highly-educated white-collar voters who have moved there and by fast-growing Hispanic populations.

But while similar demographic trends have been reshaping both states' politics, the changes have been more apparent in Virginia. Mr. Obama's 2008 victory in North Carolina was razor thin. In Virginia, however, Mr. Obama's margin of victory matched his margin nationwide almost exactly.

Virginia's political balance has shifted far enough left that it is now very close to a tipping point. In fact, it has the smallest Republican lean, 1.9 percentage points, of any state in FiveThirtyEight's Presidential Voting Index. North Carolina, by contrast, is almost eight percentage points to the right of the national average.

As Mr. Romney's polling improved nationally after the first presidential debate, North Carolina appeared to fall off the list of main battleground states . Mr. Romney is currently a 79 percent favorite to carry North Carolina, according to the FiveThirtyEight forecast. In Virginia, Mr. Obama is still favored.

Democrats there have an advantage that Democrats in North Carolina do not: The explosive growth of suburban Washington.

In 1970, Northern Virginia accounted for 12 percent of the state's population, according to the Almanac of American Politics, and 61 percent of Virginians lived in small towns and rural communities.

But in the 2010 census, one-third of Virginia residents lived in Northern Virginia. The Richmond area and the Hampton Roads region have grown too, and more than half of the state's residents live in urban areas.

No rthern Virginia now has a much greater influence in statewide elections. As the Washington suburbs have expanded, Northern Virginia has become more diverse and better educated. It is home to thousands of government workers and contractors, including many employed by defense and high-tech companies.

Northern Virginia has also become more affluent. The top 3 richest counties in the nation by median income (and 5 of the top 10) are all in the Virginia portion of suburban Washington. Loudoun County is No. 1, followed by Fairfax and Arlington Counties.

Fairfax County - the most populous in the state, with more than a million residents - has been ground zero for the demographic change, Mr. Skelley said. In 1996, Bob Dole edged out Bill Clinton in Fairfax County, and in 2000 George W. Bush beat Al Gore there. By 2008, however, Mr. Obama carried Fairfax County with slightly more than 60 percent of the vote.

Prince William County, southwest of Fairfax, has grown to more than 400,000 residents, and one-fifth of them are African-American and one-fifth Hispanic.

The Richmond area is more politically competitive, Mr. Palazzolo said. The city of Richmond is heavily African-American and Democratic-leaning, but suburban Chesterfield County to the south is Republican territory. Henrico County - which wraps around Richmond - is a tossup. There are state government employees who lean left, and the west side of Henrico looks more like Northern Virginia. But the east end of the county is more blue-collar and Republican-leaning, he said.

The Hampton Roads region, along the coast in southest Virginia, is also competitive. There are significant African-Amer ican communities in Norfolk and Hampton. But Hampton Roads is also home to a number of military installations, including Marine, Army and Air Force installations as well as the largest naval base in the world, Norfolk Naval Station. Virginia Beach, home to many active and retired military personnel, skews Republican.

Western Virginia is sparsely populated, more rural and economically depressed. It is also ruby red. The gains Democrats have made in Virginia, with a few exceptions, have been in the east.

“If anything,” Mr. Skelley said, “the western, rural part of the state has become more Republican.”

The Bellwether: Montgomery County

Montgomery County has been an almost perfect barometer of Virginia's statewide political orientation. Virginia Tech, in Blacksburg, is Montgomery County's stand-in for left-leaning Northern Virginia, while the area around the university is more Old Virginia, Mr. Skelley said.

In the past three presidential e lections, Montgomery County has never been more than one percentage point off of the statewide vote shares of the two parties.

The Bottom Line

Mr. Obama is a 71 percent favorite in Virginia, according to the current FiveThirtyEight forecast. The model projects Virginia to be on of the closest states, with Mr. Obama prevailing by 1.5 percentage points. If Mr. Romney over-performs his polling even slightly on Election Day, Virginia's 13 electoral votes will end up in the Republican column.

Mr. Obama carried Virginia in 2008 by far exceeding John Kerry's 2004 vote totals in Hampton Roads, the Richmond area and especially in the Washington suburbs.

Virginia “has moved further left since 2008,” Mr. Palazzolo said, “but Romney is more acceptable to moderate Republicans. The McCain and Palin ticket didn't sell very well with moderate Republican-leaners in Northern Virginia.”

Suburban communities, particularly in Northern Virginia, are likely to decide who carries the state again this year. Prince William, Loudoun, and Henrico Counties may prove decisive, Mr. Skelley said. All are densely populated, and all were won by Mr. Bush in 2004 and by Mr. Obama 2008.

“The candidates who can win the suburbs have always won,” Mr. Skelley said. “In recent years, the suburbs have become more liberal, which has made it easier for Democrats.”

Nov. 3: Romney\'s Reason to Play for Pennsylvania

The Saturday before the election produced a predictably large volume of polling in battleground states - but also some predictable-seeming results, with most of the polls coming close to the average of other polls.

Because President Obama leads in the polling average in most of the swing states, this means that most of the polls there on Saturday showed him ahead as well. Among the 21 polls in battleground states on Saturday, 16 had Mr. Obama ahead as compared with just two leads for Mr. Romney; three other battleground state polls had the race tied.

Some of the consistency in these results may reflect a tendency of polls to converge or “herd” around the polling average close to Election Day. This may occur because some polling firms alter their turnout models or other aspects of the polls so as not to produce outliers - a dubious practice if the goal is to provide an objective take on the race.

At the same time, Mr. Obama's state polls continue to show more strength than they did just after the Denver debate. As we wrote on Saturday, we are at the point where the polls would have to be biased against Mr. Romney (in a statistical sense) in order for him to win the Electoral College.

It is worth emphasizing the point once more that, for all the distractions caused by individual polls, the polling averages have been very reliable in the era of rich state polling.

In the table below, I have listed every instance in the FiveThirtyEight database since 1988 in which at least three polling firms issued likely voter polls in the final two weeks before an election. I have taken a simple average of the last poll that each firm re leased, similar to the Real Clear Politics method for averaging polls.

Of the 77 states with at least three late polls, the winner was called correctly in 74 cases. (I exclude Missouri in 2000, where the polling average showed an exact tie.) There has been little tendency for the state polling averages to overrate either Democrats or Republicans, or either incumbents or challengers. The state polls also performed fairly well in two years, 1996 and 2000, when the national polls were somewhat off the mark.

The chances of a miss are higher, of course, when the polls show a closer race. Even among the 33 cases where the final polling margin in a state was within five percentage points, however, the polling average identified the winner correctly in 30 cases.

The FiveThirtyEight forecast model uses a more sophisticated method than this to estimate the chance of a polling miss. For instance, it looks at how much the polls have historically missed the final margin in the election, rather than simply whether they called the winner correctly. In Ohio in 2000, for example, George W. Bush was projected to win by eight points in the polling average, but carried the state by about three points instead. That is a reasonably large error, even if it did not reverse the outcome.

Furthermore, the FiveThirtyEight estimates of the uncertainty in the polling averages are based partly on earlier years, like in 1980, in which there were few state polls but when the national polls performed poorly.

There are other characteristics of this year's polling that make upsets less likely. The polls tend to be more accurate when there are fewer undecideds in the race, and fewer voters who say they will vote for third-party candidates. The number of undecided voters is now very small in most states, and third-party candidates are not a major factor in the race (as they are in volatile polling years like 1980 and 1992).

Instead, Mr. Obama is at about 50 percent of the vote in the polling average in Pennsylvania, Wisconsin, Nevada and Michigan; at close to 49 percent in Ohio; and at about 48 percent in Iowa, New Hampshire, Virginia and Colorado.

There are not really any recent precedents in which a candidate has led by something like 49 percent to 46 percent in the final polling average, as Mr. Obama does now in Ohio, and has wound up losing the state. That does not mean such misses cannot or will not occur: there have only been a few elections when we have had as much state polling data as we do now, which is why the model allows for the possibility of a 1980-type error based on how the national polls performed that year.

But the reasonabl y high level of confidence that the model expresses in Mr. Obama's chances of winning Ohio and other states reflects the historical reality that the polling average normally does pretty well.

That brings us to Pennsylvania - where the forecast model puts Mr. Obama's chances at better than 95 percent.

One poll of Pennsylvania on Saturday, from Susquehanna Polling and Research, showed a different result, with the two candidates tied at 47 percent. But in context, this is not such a great poll for Mr. Romney.

The polling firm has had a very strong Republican lean this cycle - about five percentage points relative to the consensus, a much larger lean than firms like Rasmussen Reports and Public Policy Polling that are often criticized for having partisan results. Susquehanna is the only pollster to have shown Mr. Romney ahead in Pennsylvania at any point in the race, as they did on one occasion in February and another in October (Mr. Romney led by four points i n their previous poll of the state). Perhaps they will be proven right, but it is usually a bad bet to bank on the one poll rather than the many.

Still, Mr. Romney's campaign is making a late play for Pennsylvania with advertising dollars and a visit there on Sunday.

That is probably a reasonable strategy, even though Mr. Romney's chances of pulling out a victory in Pennsylvania are slim. What makes it reasonable is that Mr. Romney's alternative paths to an Electoral College victory are not looking all that much stronger.

Wisconsin, for instance, is one of the states where Mr. Obama has shown the sharpest rebound in his polling. Another issue for Mr. Romney is that Wisconsin allows voters to register on Election Day, which may make it one case where the likely voter models that pollsters apply are too restrictive. Polls put out by two Wisconsin-based universities, St. Norbert College and Marquette University, show a larger lead for Mr. Obama than those prod uced by national polling firms, which may not account for these nuances. (Democrats slightly outperformed the polling average in Wisconsin in both 2004 and 2008.)

Nevada is problematic for Mr. Romney because perhaps 65 or 70 percent of its vote has already been cast - and because Democrats have roughly a 50,000-ballot lead there based on the votes that have been collected so far. The better news for Mr. Romney is that Democratic margins in the early vote count are down from 2008. But Mr. Obama carried Nevada by more than 12 percentage points that year, so he could lose a significant amount from his margin and still win.

Democrats also have about a 63,000-ballot lead in Iowa based on the early vote. That is down from an 87,000-ballot lead for Democrats in 2008. Still, as in Nevada, this is a state where Mr. Obama can afford to lose something from his 2008 margin, when he won Iowa by about 10 percentage points.

Ohio is another early-voting state. The most rec ent figures in Democratic-leaning Cuyahoga County, home to Cleveland, suggest that about 236,000 votes have already been cast there, representing 35 percent of 2008 turnout.

In Franklin County, where Columbus is the largest city and which is the Democrats' next best county in the state, early votes represent 36 percent of 2008 turnout.

By comparison, the early vote represents 21 percent of 2008 turnout in the other 86 counties in Ohio, combined.

Unlike in Iowa and Nevada, where the early-voting numbers favor Democrats but are down from 2008, the statistics in Ohio could wind up being quite similar to those from 2008 once the last two days of early balloting are concluded on Sunday and Monday.

In 2008, 39 percent of the vote was cast early in Cuyahoga County and 44 percent in Franklin County, compared with 22 percent elsewhere in the state.

The early-voting figures in these states tell a story that seems to be consistent with the polling. In cont rast to Iowa and Nevada, where Mr. Obama will almost certainly underperform his 2008 margins, the polls anticipate less of a decline for Mr. Obama in Ohio, which he won by five percentage points four years ago.

My inference, then, is that Mr. Romney's campaign may be thinking about a map like this one, in which he wins Pennsylvania in order to claim 273 electoral votes. If Mr. Romney did so, he could win the presidency despite losing Ohio, Wisconsin, Iowa and Nevada.

Mr. Romney could not afford to lose Virginia, where he is narrowly behind in the polling average, or Florida, where he is narrowly ahead. He could also not afford to lose Colorado, unless he won New Hampshire.

But Florida, Virginia an d Colorado are traditionally slightly Republican-leaning. If Mr. Romney overperforms his state polls across the board - something he will need to do anyway to win the election - they may come along for the ride.

Is Mr. Romney likely to flip enough votes in Pennsylvania to win? Probably not. Pennsylvania has historically had quite accurate polling, with the final polling average missing the eventual margin there by just one percentage point on average between 1996 and 2008. It is also a relatively “inelastic” state, meaning that there are relatively few swing voters who make up their minds at the last minute - perhaps part of the reason that the polling has normally been accurate.

Given the number of unappealing options for Mr. Romney, however, it may be worth a try. Pennsylvania still ranks seventh on the FiveThirtyEight list of tipping-point states - and that is without considering the mechanics of early voting. Pennsylvania has little early voting, meaning that a larger share of the vote there is still in play.

We will still be watching for more swing state polling later on Sunday and on Monday, but the final national polls will also deserve attention.

On Sunday, Mr. Obama led by an average of about one percentage point among seven national surveys. That is not much of an edge, but better than had generally been the case for him just after the Denver debate.

What Mr. Romney will want to see are national polls showing him a point or so ahead in the race, as was the case just after Denver.

If the national polls show a tie on average, then Mr. Romney will be more of an underdog than you might think, since that is when Mr. Obama's Electoral College advantages will tend to give him their greatest benefit. In the FiveThirtyEight simulation on Saturday, Mr. Obama won the Electoral College about 80 percent of the time when the national popular vote was tied.

Nov. 2: For Romney to Win, State Polls Must Be Statistically Biased

President Obama is now better than a 4-in-5 favorite to win the Electoral College, according to the FiveThirtyEight forecast. His chances of winning it increased to 83.7 percent on Friday, his highest figure since the Denver debate and improved from 80.8 percent on Thursday.

Friday's polling should make it easy to discern why Mr. Obama has the Electoral College advantage. There were 22 polls of swing states published Friday. Of these, Mr. Obama led in 19 polls, and two showed a tie. Mitt Romney led in just one of the surveys, a Mason-Dixon poll of Florida.

Although the fact that Mr. Obama held the lead in so many polls is partly coincidental - there weren't any polls of North Carolina on Friday, for instance, which is Mr. Romney's strongest battleground state - they nevertheless represent powerful evidence against the idea that the race is a “tossup.” A tossup race isn't likely to produce 19 leads for one candidate and one for the other - any more than a fair coin is likely to come up heads 19 times and tails just once in 20 tosses. (The probability of a fair coin doing so is about 1 chance in 50,000.)

Instead, Mr. Romney will have to hope that the coin isn't fair, and instead has been weighted to Mr. Obama's advantage. In other words, he'll have to hope that the polls have been biased in Mr. Obama's favor. (I recognize that ‘bias' is a loaded term in political contexts. I'll explain what I mean by it in a moment.)

There are essentially three reasons that a poll might provide an inaccurate forecast of an upcoming election.

The first is statistical sampling error: statistical error that comes from interviewing only a random sample of the population, rather than everyone. This is the type of error that is represented by the margin of error reported alongside a poll and it is reasonably easy to measure.

If you have just one poll of a state, the statistical sampling error will be fairly high. For instance, a poll of 800 voters has a margin of error in estimating one candidate's vote share of about plus or minus 3.5 percentage points. In a two-candidate race, however, the margin of error in estimating the difference between the candidates (as in: “Obama leads Romney by five points”) is roughly twice that, plus or minus seven percentage points, since a vote for one candidate is necessarily a vote against the other one.

The margin of error is much reduced, however, when you aggregate different polls together, since that creates a much larger sample size. In Ohio, for example, there have been 17,615 interviews of likely voters in polls conducted there within the past 10 days. That yields a margin of error, in measuring the difference between the candidates, of about 1.5 percentage point - smaller than Mr. Obama's current lead in the polling average there.

In other words, Mr. Obama's current lead in Ohio almost certainly does not reflect random sampling error alone. The same is true in states like Iowa, Nevada, Wisconsin and others that would suffice for him to win 270 electoral votes. (Mr. Obama's more tenuous leads in Colorado and Virginia, and Mr. Romney's thin lead in Florida, potentially could be a product of sampling error.)

So why, then, do we have Mr. Obama as “only” an 83.7 percent favorite to win the Electoral College, and not close to 100 percent?

This is beca use of the other potential sources of error in polling. One is that a poll is a snapshot in time - even if you're sampling the voters accurately, their opinions could change again before Election Day.

This is a huge concern if, for instance, you're conducting a poll in June of an election year. Michael Dukakis led the polls for much of the spring in 1988; John Kerry did so for some of the summer in 2004; even John McCain, in 2008, had a few moments when he may have been ahead in the polling average.

But it's now the weekend before the election. The vast majority of voters are locked into their choices. In some states, in fact, a fair number of them have already voted. (Perhaps about 20 percent of the vote nationwide has been cast, and the tally may be as high as two-thirds of the vote in some states like Nevada.)

Nor are there any more guaranteed opportunities for news or campaign events to intervene to alter the dynamics of the campaign, at least not at th e national level. The debates have been held; the conventions occurred long ago; the vice-presidential nominees have been picked. The last major economic news of the campaign came on Friday, with the release of the October jobs numbers. A negative print on the payrolls report, or a sharp rise in the unemployment rate, could have altered the campaign, but instead the jobs report was a pretty good one. (I don't expect the jobs report to produce much of a boost for Mr. Obama, but there's little in the report that would aid Mr. Romney.) The recovery from Hurricane Sandy is still a developing story, but not one that seems to be playing to Mr. Romney's benefit.

There is the remote possibility of a true “black swan” event, like a national-security crisis or a major scandal unfolding at the last minute, but the chance for news events to affect the campaign is now greatly diminished. And most of the polls that we've seen over the past several days are the last ones that pol ling firms will be releasing into the field.

That leaves only the final source of polling error, which is the potential that the polls might simply have been wrong all along because of statistical bias.

Polling is a difficult enterprise nowadays. Some estimate that only about 10 percent of voters respond even to the best surveys, and the polls that take shortcuts pay for it with lower-still response rates, perhaps no better than 2 to 5 percent. The pollsters are making a leap of faith that the 10 percent of voters they can get on the phone and get to agree to participate are representative of the entire population. The polling was largely quite accurate in 2004, 2008 and 2010, but there is no guarantee that this streak will continue. Most of the “house effects” that you see introduced in the polls - the tendency of certain polling firms to show results that are consistently more favorable for either the Democrat or the Republican - reflect the different assum ptions that pollsters make about how to get a truly representative sample and how to separate out the people who will really vote from ones who say they will, but won't.

But many of the pollsters are likely to make similar assumptions about how to measure the voter universe accurately. This introduces the possibility that most of the pollsters could err on one or another side - whether in Mr. Obama's direction, or Mr. Romney's. In a statistical sense, we would call this bias: that the polls are not taking an accurate sample of the voter population. If there is such a bias, furthermore, it is likely to be correlated across different states, especially if they are demographically similar. If either of the candidates beats his polls in Wisconsin, he is also likely to do so in Minnesota.

The FiveThirtyEight forecast accounts for this possibility. Its estimates of the uncertainty in the race are based on how accurate the polls have been under real-world conditions sin ce 1968, and not the idealized assumption that random sampling error alone accounts for entire reason for doubt.

To be exceptionally clear: I do not mean to imply that the polls are biased in Mr. Obama's favor. But there is the chance that they could be biased in either direction. If they are biased in Mr. Obama's favor, then Mr. Romney could still win; the race is close enough. If they are biased in Mr. Romney's favor, then Mr. Obama will win by a wider-than-expected margin, but since Mr. Obama is the favorite anyway, this will not change who sleeps in the White House on Jan. 20.

My argument, rather, is this: we've about reached the point where if Mr. Romney wins, it can only be because the polls have been biased against him. Almost all of the chance that Mr. Romney has in the FiveThirtyEight forecast, about 16 percent to win the Electoral College, reflects this possibility.

Yes, of course: most of the arguments that the polls are necessarily biased agains t Mr. Romney reflect little more than wishful thinking.

Nevertheless, these arguments are potentially more intellectually coherent than the ones that propose that the race is “too close to call.” It isn't. If the state polls are right, then Mr. Obama will win the Electoral College. If you can't acknowledge that after a day when Mr. Obama leads 19 out of 20 swing-state polls, then you should abandon the pretense that your goal is to inform rather than entertain the public.

But the state polls may not be right. They could be biased. Based on the historical reliability of polls, we put the chance that they will be biased enough to elect Mr. Romney at 16 percent.