You can say what you want about who is the best candidate for president, but one thing, to me, is certain: Obama is the candidate of change. No one can reasonably hold, due to a plethora of empirical evidence, that McCain will not closely follow Bush's policies. This is, I think, central question: do you think that we need a change of leadership in the US from GW. I think the answer will come out as voters will want change and that this is the central reason Obama will win this election.
Here is some evidence that it is a slam dunk.