What a difference a disaster makes.

Where last week President Obama was listless, passive, crotchety, tonight in New York he had a noticeable spring in his step. A swagger, even. In what may turn out to be the most replayed snippet of all three debates, Obama invited Mitt Romney to attack him over the administration’s handling of the attack on the U.S. diplomatic mission in Benghazi. “Please proceed, governor,” he said, cockily. Romney bungled the attack — the low-information viewer was led to believe Obama and his staff were never in doubt the attack was planned and perpetrated by terrorists — and even managed to praise the president for taking responsibility for it.

Romney’s was an unforgivable whiff. Surely he is kicking himself as I write. (A lot of conservative ire on this exchange will be directed at CNN moderator Candy Crowley. In her defense, I think she attempted balance in her intervention; she noted that the president used the words “act of terror” but also defended Romney’s assertion that the administration continued to peddle the “spontaneous demonstration” canard.)

But this election is not, fundamentally, about Libya. It’s about the state of the economy. And on this question Romney was on his game. Perhaps not as crisply or as confidently as he was in Round 1. But for two minutes that seemed like five, Romney unleashed a torrent of horrible data on unemployment, underemployment, food stamps, poverty rates, and exploding deficits. There is little that can be said to deny it or affirmatively defend it. The record is there, and Obama is lumbered with it.

Make no mistake, though: the president countered Romney effectively tonight — much more so than he did in the first debate (which is to say, almost not at all). He issued a line about Romney’s tax plan — “sketchy deal” — that may come to equal 2000-era Al Gore’s “risky scheme” in the annals of rhetorical barbs.

Obama pressed hard to recapture women; he brought up contraception, wrapped into a general riff on women’s health and tied it to a narrative about families’ economic security. I don’t agree that the HHS mandate is an unprecedented act of tyranny, but I do believe it’s an unnecessary federal intrusion. And obviously, Obama wasn’t aiming at me. Did it work? I wish I could tell you.

The question is this: how much of Obama’s slide in the polls owes to Romney having swayed undecided voters, and how much owes to diminished Democratic enthusiasm? To the extent that it’s the latter, Obama helped himself tremendously tonight. To the former, I would say quite a bit less so.