Why Last Night Mattered

I'm going to stick with my hunch and reiterate that last night was a key win for Obama. Why? Chuck Todd explains:

He proved that he belonged on the same stage as Clinton. And that's an important accomplishment, because you keep wondering whether undecided voters are waiting to see if Obama can prove his mettle for the presidency. There's a theory that believes just that. And if that theory is true, then last night's debate could prove to be very important to Obama. The audience was undecided voters and former Edwards supporters, and we're guessing these folks have a fairly low bar for Obama to prove himself to them, compared to the bar they have for Clinton since they are still not on board with the more well-known candidate.

It's what Mark Blumenthal identifies as the "readiness" question. Last night, Obama made huge gains on that question. And Edwards' withdrawal made it possible.