Of course, exit polls aren't always reliable (and in 2004, as we all remember, something funny happened between the exit polls and the final vote-count). But the following items, reported by Ben Smith of Politico, do seem like interesting straws in the wind:
ABC calls Pennsylvania and New Hampshire for Obama, based on the exit polls; CNN is waiting to project.That's a big "if" at the beginning of the second paragraph. It really has looked for weeks as though the McCain campaign's effort to capture Pennsylvania was based on wishful thinking (or desperation) more than anything else, so I will be surprised if Obama doesn't carry Pennsylvania in the end. New Hampshire would be a more interesting (though hardly astonishing) result.
If ABC is right, that's more or less the ballgame. Without those two states, the scenarios for McCain become increasingly exotic: He needs to win in Western states he's losing, or he needs to steal a state in the upper Midwest.
The big East Coast battleground state from which the exit polls might really be (more or less) definitive would be Virginia. If McCain loses Virginia, and especially if he seems to be losing it decisively, then I think one really could conclude that his chances of getting elected are hopeless.
I don't think there is any strong evidence available yet on which way Virginia will go. But a post on the WSJ blog does mention an interesting tidbit that may provide some indirect signs:
And while Virginia voters in 2004 were more Republican than Democratic, 39% to 35%, this year Democrats outnumber Republicans at the polls, 41% to 32% – a 13-point swingI guess within a few hours we'll know better what that means.