Actually, most of his wins were by margins of either 10% or above. I think only a couple of his were within single-digit margins. The latter seems to be the rule when it comes to Clinton's wins, however.

Clinton's campaign has been negative primarily because all she's been running on the illusions of her name and supposed 'experience'. I can't think of a time when Clinton doesn't meet the opportunity to jab him in the side. As for dirty, I know a number of different fabrications and diversions that were spread and in some instances started by the Clinton campaign; the whole Obama-is-a-secret-Muslim email chain, the Canada/NAFTA fiasco, and the reverend flap are just a few that come to mind. While Clinton seems to throw out the smelliest shit and hopes it sticks, the only thing 'dirty' coming from Obama seemed to be his defenses of the shit being thrown at him.

I think Americans are largely tired of the Clinton's, and especially with the de facto dynastic politics. Obama certainly isn't perfect, and I highly doubt he will be much of a revolution to the political structures in Washington, but he certainly is a breath of fresh air compared to Clinton.

It seems you're getting your hopes up, then.