There’s no point in putting it gently: Mitt Romney had one of his worst polling days of the year on Wednesday.
We’re at a point in the race, however, when it’s important to contrast what we think might happen on Nov. 6 with what we’re seeing in the polls at the moment. Right now, there is a gap between these two things.
Although Mr. Obama is now the clear favorite in the Nov. 6 forecast, his advantage is larger in the FiveThirtyEight “now-cast,” which projects what would happen in an election held today.
The “now-cast” estimates that Mr. Obama would have a 97.8 percent chance of winning an election held today. Further, it pegs his advantage at five and a half percentage points in the national popular vote.
By contrast, the Nov. 6 forecast expects Mr. Obama to win by a smaller margin, 3.6 percentage points, on Election Day itself.
Right now, the Nov. 6 forecast projects that Mr. Obama will win the popular vote by 3.6 percentage points. As I mentioned, that does account for about a two-point decline from where Mr. Obama seems to be in the polls right now. Otherwise, however, the model assumes that the uncertainty in the forecast is symmetric: Mr. Obama is as likely to overperform it as underperform it.
If Mr. Obama misses to the downside by 3.7 percentage points, then Mr. Romney would win, at least in the popular vote. However, if Mr. Obama missed to the upside by 3.7 percentage point instead, he’d win the popular vote by 7.3 percentage points, exactly replicating his margin from 2008.
In other words, there looks to be about a 20 percent chance that Mr. Romney will win, but also about a 20 percent chance that Mr. Obama will actually beat his 2008 margin in the popular vote. The smart money is on an outcome somewhere in the middle – as it has been all year. But if you can conceive of a Romney comeback – and you should account for that possibility – you should also allow for the chance that things could get really out of hand, and that Mr. Obama could win in a borderline landslide.