Yes, he has to flip every swing state, but if there's a perfect storm, he can do it. First, the Bradley Effect would have to be real in most swing states, and be compounded with the general tendency of polls to favor the Democrats, just as they favored Gore and Kerry. Then, the expectations that young and new voters will turn out much more than usual would have to be illusory. All the conservatives who have been claiming they can't vote for McCain, but who hate Obama, would have to go to the polls and vote for McCain. Then the election might be close enough for the Republicans to steal it, once again.