The initial polls show Obama looking more likable, in touch, and presidential in the first debate. This one was supposed to be John McCain's best one. James Fallows highlights a difference in strategy between the two candidates that gave Obama the upper hand, specifically that Obama actually had one while McCain's only focusing on the short term.
Of course, it doesn't help when you can't even maintain composure enough to refrain from saying "horseshit" in the middle of a nationally televised debate:
Perhaps not coincidentally, this weekend Barack broke 50% in three of the big five national polls (including Gallup) for the first time.