In last night's now semi-famous Hardball segment, Mark Penn fingered this Oct. 28 New York Times article--in which Obama offered a "vow to go on the offensive" against Clinton--as the start of all the negativity. But in fact Obama only grew slightly tougher, mainly by harassing Hillary over her Iran position. It was John Edwards who went hard at Hillary's trustworthiness and character this fall, before backing off for the home stretch. If Obama winds up beating Hillary, he may have Edwards to thank for doing the pivotal dirty work for him.
P.S. Of course, it may turn out that the man who really turned the election was... Chris Dodd! It was Dodd who exposed Hillary's immigrant-licenses dodge in the Philadelphia debate, a moment which decisively changed the narrative of the unstoppable flawless Clinton campaign.