Joe Klein’s report from the final weekend of stumping in Pennsylvania is well worth reading. This observation would particularly worry me if I was the Obama campaign: Energy: Obama seems either bummed or pissed or exhausted. He could be near death and still be a pretty good speaker, but he's very much off his game right now. Clinton, by contrast, is on fire--as energetic and passionate as I've seen her.
One of the oddities of this campaign is that Obama—by far the youngest candidate—tires more easily, or at least more visibly, than anyone else running. Indeed, Obama has blamed the most spectacular misstatement of the election so far on his tiredness.