Oct. 10: Is Romney Leading Right Now?
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[new article] Oct. 10: Is Romney Leading Right NowOct. 10: Is Romney Leading Right Now?
By NATE SILVER
Polling since the debate in Denver last week has generally been very strong for Mitt Romney. But there have also been a couple of rays of hope for Democrats and President Obama.
One hypothesis is that Mr. Romney’s debate bounce was initially very strong, but has since faded some. There is a case to be made for this — but Wednesday’s polling made it weaker.
Although Mr. Romney’s standing declined by two points in the Gallup national tracking poll, he improved slightly in four other tracking surveys, from Rasmussen Reports, Ipsos, Investors’ Business Daily and the RAND Corporation. And the state polling data that came in on Wednesday wasgenerally consistent with about a three-and-a-half-point bounce for Mr. Romney, similar to previous days.
There is some spotty evidence that Mr. Romney’s bounce may have been as large as five or six points in polls conducted in the 48 hours after the debate, so perhaps the most recent data does reflect something of a comedown for him. But if his bounce started out at five or six points and has now settled in at three or four, that would still reflect an extremely profound swing in the race — consistent with the largest shifts produced by past presidential debates. We’ll see what happens once the news cycle turns over, such as afterThursday’s vice-presidential debate.
For the time being, however, Mr. Romney continues to rocket forward in our projections. The forecast model now gives him about a one-in-three chance of winning the Electoral College (more specifically, a 32.1 percent chance), his highest figure since Aug. 22 and more than double his chances from before the debate. Mr. Romney may have increased his chances of becoming president by 15 or 20 percent based on one night in Denver.
The more troubling sign for Mr. Romney, however, is that although he’s made gains, he does not seem to have taken the lead in very many state polls. That trend, if anything, has become more entrenched. Of the half-dozen or so polls of battleground states published on Wednesday, none showed Mr. Romney ahead; the best result he managed was a 48-48 tie in a Rasmussen Reports poll of New Hampshire.
The more troubling sign for Mr. Romney, however, is that although he’s made gains, he does not seem to have taken the lead in very many state polls. That trend, if anything, has become more entrenched. Of the half-dozen or so polls of battleground states published on Wednesday, none showed Mr. Romney ahead; the best result he managed was a 48-48 tie in a Rasmussen Reports poll of New Hampshire.
(We ran the model on Wednesday before the latest polls from Marist College, The Philadelphia Inquirer, or The New York Times, Quinnipiac University and CBS News were published overnight, which were also suggestive of a narrow advantage for Mr. Obama in the majority of swing states.)
How to reconcile this against the fact that Mr. Romney is about tied — or perhaps even has a small lead — in the average of national polls right now?
From a forecasting standpoint, this is the question that the whole election may turn upon. There are basically four ways to explain the difference.
1) This is a statistical quirk that will work its way out of the system.
2) Mr. Obama has some pronounced advantage in the Electoral College relative to his position in the popular vote.
3) The state polls systematically overestimate Mr. Obama and underestimate Mr. Romney.
4) The national polls systematically overestimate Mr. Romney and underestimate Mr. Obama.
2) Mr. Obama has some pronounced advantage in the Electoral College relative to his position in the popular vote.
3) The state polls systematically overestimate Mr. Obama and underestimate Mr. Romney.
4) The national polls systematically overestimate Mr. Romney and underestimate Mr. Obama.
Could State-National Differences Be a Statistical Fluke?
The first proposal — that this simply reflects statistical noise — may be part of the answer, but I don’t know that it’s a sufficient explanation on its own. Since the Denver debate, there have been on the order of 12,000 people surveyed in national polls, and a similar number in the battleground states. The theoretical margin of error on a 12,000-person sample is about 1.8 percent in reflecting the difference between the two candidates.
If it just so happens that the set of national polls have been a positive outlier for Mr. Romney and the state polls have been a negative outlier for him, then perhaps you can explain the whole of the discrepancy. But that explanation would be more compelling had these differences not also been apparent formost of the election cycle.
An Electoral College-Popular Vote Split?
The second answer is the most intuitively satisfying, and would make the boldest assertion: that in an election held today, Mr. Obama would be favored to win the Electoral College but would probably lose (or at best roughly tie) the popular vote. However, there are several powerful rebuttals to it.
First, splits between the Electoral College and the popular vote are historically very uncommon.
Second, the swing states are swing states for a reason: because they resemble (certainly collectively, if not also individually) the American electorate as a whole. There are a lot of voters in the nonbattleground states who are demographically similar to those in Ohio, Florida, Virginia or Colorado. (If Mr. Obama is performing well in Ohio, then it should figure that he’s also performing well with Ohio-like voters in noncompetitive neighboring states like Indiana or Kentucky, for example.) The set of swing states is also quite geographically diverse, covering almost literally the four corners of the country.
Third, the campaigns have been roughly equal in their advertising spending this year. If one campaign had an especially heavy resource advantage in the swing states (as Mr. Obama may have had in 2008), then perhaps this explanation would make more sense.
Fourth, this hypothesis depends implicitly on the idea that Mr. Obama, if he is overperforming in the swing states, must also be underperforming in the other states. Although there hasn’t been much polling outside the battleground states recently, the evidence from the polling before the debate was not very supportive of this idea. If anything, for example, Mr. Obama seemed to be performing comparatively well in deeply red states, seeing little drop-off from his 2008 results. Perhaps fresher evidence will lend more credibility to this hypothesis (one poll on Wednesday showed Mr. Obama’s margin falling substantially in California, for instance). But it hasn’t been that convincing up to this point in time.
None of this means that this case is completely without merit. Our forecast model does infer that Mr. Obama has a very slight Electoral College advantage. (As of Wednesday, it gave him a 67.9 percent chance of winning the Electoral College against a 66.7 percent chance of winning the popular vote.)
But some of our competitors are issuing forecasts suggestive of a very largedifference between the Electoral College and the popular vote — to a degree that is frankly not credible, in my view. (We’ll compare the FiveThirtyEight forecasts against some alternatives in a moment.)
Reasons to Prefer National Polls to State Polls
There are some reasons to prefer national polls to state polls. First, they probably come from slightly stronger polling firms on average and they often have larger sample sizes, although there are exceptions on either side.
Second, they’re more straightforward to interpret — especially if you want to derive an estimate of how the national popular vote will break down. The alternative requires you to “add up” the polls from individual states, as well to estimate what share of the national turnout each state will represent.
