His candidacy is a bet that the American people are sick of the Republican propaganda machine's nasty, polarizing effect on the political process, and that it's possible to rise above that process, to run as a voice of moderation, and win.
Clinton is the candidate of winning the game, Obama is the candidate of changing the game.
Obama's powerful “bringing America together” rhetoric — and his mushiness on policy — are both characteristic of this approach. What does Obama stand for? It's hard to tell, beyond changing the style of American politics. But right now changing the style of American politics is a worthwhile goal. The question is whether it will work, and I go round and round about that. It may be that Obama is simply naïve, and that the Republicans will find a way to slime him too and make his ploy impossible. But with a deeply unpopular Republican President and weak Republican candidates, this year may be the best opportunity we'll get to change the face of American politics.
Almost nine months later, we have Obama being very clear about policy ... and mostly offering up some impressive thinking. But more importantly, we have this:
These are people who have been driven out of the Republican party, rather than who have been drawn to the Democrats ... but in Obama they see a Democrat they can vote for.
Eric Hirshberg talks about the interviews in that clip.