The new FiveThirtyEight column went up about an hour ago and it's no surprise. You can read it here. He restates the case for calling President Obama the favorite. But, for my money the best part is how he debunks the Mitt-mentum meme.
Here is his explanation for the chart he created that graphically demonstrates how this line of thinking simply fails to hold up to scrutiny.
In the table below, I’ve listed the polling averages in the most competitive states, and in the national polls, across several different periods.And then here's the chart
First are all polls from June 1, the approximate start of the general-election campaign, until the start of the party conventions.
Next are the polls between the conventions and the first debate in Denver in early October.
Finally are the polls since that first debate in Denver. It’s been roughly 30 days since then. If Mr. Romney has the momentum in the polls, then this should imply that his polls are continuing to get better: that they were a little better this week than last week, and a bit better last week than the week before. So these polls are further broken down into three different periods of about 10 days each, based on when the poll was conducted.
What type of polling average is this, by the way? About the simplest possible one: I’ve just averaged together all the polls of likely voters in the FiveThirtyEight database, applying no other weighting or “secret sauce.”