He's obviously supported Obama for some time now. Why else would he feel the need to defend Obama as if he was another talking head on the Obama campaign PR circuit. As for his uneasiness with the Republican party's shift to the right... I think the fact that McCain is the nominee puts the idea to rest. Notta word though, 'bout the Democrats' shift to the left.
A lot of people respect General Powell's words, which is why Obama and Powell are banking on just that, hoping this gives Obama a much needed cushion.