Hillary Clinton is also not a very exciting, inspiring candidate to a lot of the left-leaning Democratic base, especially in Iowa.

[Hillary] Clinton has also struggled with key groups of voters.

The enthusiasm for [Donald] Trump had gone up. The net result was it made people more supportive of him.

Jeb Bush was supposed to be the establishment candidate, but he didn't catch on. And the extraordinary thing about this Republican primary is that the establishment, moderate wing of the party has sidelined itself. They're not coalescing around one candidate as they have in the past.

Both the Obama and Romney campaigns said they pulled all their political ads today in observance of the September 11th anniversary. But politics wasn't very far offstage. The Obama campaign sees foreign policy as an advantage this year.

Romney still enjoys the Republicans' traditional advantage among voters who are veterans, but the Obama campaign is confident it can chip away at that.

If [Hillary] Clinton wins, history will also be made: She would be the first female U.S. president, of course, but also the only candidate in the modern era, other than George H.W. Bush, who managed to follow a two-term president of her own party.