Like I said before, these polls are likely to do all sorts of gyrations before election day and they don't matter as much as we may think since as Al Gore can tell you, it's the electoral college that matters.
That USA Today/Gallup poll showing Sen. McCain with a 4% lead used a likely voter model of 10% turnout by the youth vote. Okay, let's assume that there's no Obama effect on the youth vote (and Sen. Clinton can probably tell you that that isn't true), the youth vote was still 16% in 2004! Does anyone seriously think the youth vote is going to decrease by that much? In all likelihood the number will go up, and the vast majority will be Obama voters. So, even in a poll that I concede is not exactly a great predictor, Sen. Obama's number is being underestimated.
Then again, keep those numbers jimmied in the polls, pollsters. Let the surprise come on election day.