Reid Wilson suggests that this will be a "classic mobilization election," where base turnout matters more than persuading the "undecided middle." Chait analyzes:
This would explain why Obama’s campaign has devoted the vast bulk of its resources to turning out its base. It would also explain why polls have produced such divergent shares of the nonwhite vote. The pollsters’ challenge is to guess how many nonwhite voters will show up. Obama’s is twofold: First to make sure it has found them, and then get them to do it.
The Dish 