His knockout punch is surely the excitement and hope he has unleashed across cultural divides amongst the Democratic base- including many that are, traditionally, not Voters at all. Whilst refusing to bow to the old Lobby groups by accepting money from big Oil, big Pharma and several other dubious funding sources. Plus his electoral 'weakness'- Catholic White boys who play bowls in rust belts (slightly taking the piss) are both a declining demographic, and often wont to vote conservative anyway. Yesterdays heroes.
Meanwhile his underfunded competitor just brings the debate lower, and will accept money (and hence obligation) from anywhere. I think most Americans should be able to see this.
It's already been the case, I have read, that card carrying Repub's have been voting for Hillary in some primaries to drag on her campaign as long as possible, and let Mccain bask in the shadows for as long as possible. Hillary, of course, doesn't mind. I honestly think it's more important to her to win the nominaton than that the Democrats win the Presidency. She expected a cakewalk to the Dem nomination, and resents the temerity and popular appeal of Obama bitterly.