Nate Silver in the NYT:

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.