It's pretty clear that Obama went into last night's debate with a very clear strategy.
It was this:
a) Stay above the fray. If Romney was looking at this as an opportunity to sling zingers and create "moments," Obama would do the opposite. He'd be calm, professional, presidential.
b) Keep the focus on Romney's tax and Medicare plans, pointing out the lack of specifics and the danger to the middle class.
Obama wanted to come out of the debate winning the personality contest (he's the guy you'd rather hang out with) and solidifying specific parts of the Romney narrative.
He clearly didn't want to solidify other aspects of the Romney narrative -- namely, the 47%, Bain outsourcing and tax returns -- because going there would fight against his first objective, to be the most reasonable and likable person onstage.
Not a horrible strategy, overall, though certainly a very safe one. This was Obama playing prevent defense. (But, as football fans like to say, the only thing the prevent defense prevents is winning).
The problem is that a different Romney showed up than the one Obama's team expected, and Obama couldn't (or chose not to) adjust his strategy.
Romney flat out lied about his own plans (and Obama's). He shifted to the center, even claiming he wouldn't cut taxes on the right. And Obama let him get away with it, only once feebly calling him out with his "never mind" comment.
To stay with the football metaphor, it's as if Obama fielded a short-yardage defense only to see Romney line up with five wide receivers. And instead of calling a timeout and changing the personnel, Obama kept trying to stop the run.
I certainly hope Obama and Co. learn from this mistake, and history suggests they will. I want to see him more aggressive in the next debate (and in the next several days of response to this one).
Call Romney out as a liar. Call him out as a man who will say whatever anybody wants to hear because he has no core beliefs. Don't be afraid to fight. That doesn't diminish your stature, it strengthens it.