If Obama wins the Presidency, we won't look back on this debate as the moment he did it, as my disgruntled colleague suggests. But he didn't lose it tonight. Obama was much better prepared. It may have been the first time in his life he actually had to study for an exam. He spent a lot less time looking at his shoes.
Romney was pretty much the same guy who showed up at the first debate: well informed, reasonably quick on his feet, a little over excited and repetitive at times. He did a very good job of focusing on Obama's dismal economic record, though not as good as I think he could have done. I thought Romney was a head slightly through most of the debate until the Benghazi question. At that point the advantage turned to Obama and he held onto it.
Obama ducked the question and gave us a lot of highly peppered word salad. Romney could have pointed that out, saying something like: if I ever have to answer such a terrible question, I won't try to avoid it. He could have laid out the simple fact that the Administration couldn't get its story straight for weeks. He could have pointed out that the Administration's idea of dealing with the debacle was go after an idiot who made a film that had nothing whatsoever to do with the murder of the Ambassador.
But he didn't. He got bogged down over the word "terrorist" and that allowed Obama to slip out of the net. Jon is dead spot on about moderator Candy Crowley's interjection at that point. It was inexcusable. It was not her job to take sides or correct either participant. And as Jon said, she was clearly wrong.
All that said, I think Obama might actually suffer from Romney's failure on the Benghazi question. Every story about the debate is going to mention the question and thus keep the issue on the front pages for days more. If Romney had a stronger answer, it would actually be easier for the sympathetic press to ignore it.
I am guessing that this debate marginally helps Obama in so far as he recovered from the first one. That helps shore up his base. I don't see any reason to expect that it will do more than that.
Update: I withdraw the word "disgruntled" above.
Update: as Jon notes, the CNN spot poll gives the win to Obama but the issues to Romney. He wins big on the economy (58/40), taxes (51/44), and marginally on health care and "strong leader". If that is really what the voters take away from this debate, Romney wins big again.