I wouldn't be so sure about the Powell endorsement rumors. I'm with Ambers on this. It's too ballsy a move for Powell. I'm also inherently suspicious of Kristol's motives. If Powell were considering such an endorsement, Kristol would do all he can to derail it. Prematurely leaking it, creating a fire-storm and forcing Powell to deny is one way to pre-empt such a move. It's vital for the neocons to prevent Obama gaining traction with serious foreign policy machers.
But it makes sense in one obvious way: Powell understands how deep a hole the US is in internationally, and how only Obama truly has a chance to get the country back on its feet. It's the impulse of a patriot. And maybe the smears have made him mad.