Obama is taking some lumps right now, but he's quietly building up an effective ground game and raising trainloads of money for the fall. There's no need to panic over a few days of weak polling. I still say he wins the general election by 6-8 points.
UPDATE: I guess I should add that my relative optimism is based on my belief that Obama and his campaign team aren't morons. Time will tell on that front, of course, but so far they've struck me as a pretty savvy bunch.