More than anything else, we strongly believe in three predictive indicators, all of which suggest that the president will lose the popular vote. First is his current vote share, which stands at approximately 47-47.5 percent. Incumbents rarely improve on their final poll numbers by more than one or two points, putting Obama at approximately 48-49 percent on Election Day.
Second, Romney has more than a 10-point lead among Independents nationally and in most key swing states. Our average of national polls fielded over the last two weeks shows Romney with a 14-point lead among Independents. For context, that’s a full six points better than Obama’s eight-point advantage over McCain in 2008. …
Which leads to the third point: voter enthusiasm and energy is with the GOP. A recent Pew poll had Republicans with a 14-point lead over Democrats in terms of vote likelihood.
Put these three elements together — Obama’s current vote share, Romney’s lead among Independent voters and overall GOP enthusiasm — and it strongly suggests that Romney will win the popular vote.