No, it's not the unemployment rate.
OK, the debate's over. President Obama did a poor job, Mitt Romney did well, and facts and arguable misstatements got lost amid the unavoidable focus on performance skills.
Where does that leave us?
If you go to one of the academics who really studies elections, then, well, you'd best count to ten, maybe to 10,000, and look far beyond the debate to see how the election will play out. It is about the economy, stupid, and a few matters related to it.
"I form my expectations from five different structural factors that empirical research indicates are the main influences, election in and election out," said John Mark Hansen, a political scientist and former dean of social sciences at the University of Chicago. "They are the economy, condition of foreign affairs, the policy positions of the two nominees relative to the electorate, the baseline partisanship of the electorate, and incumbency."
What matters in foreign affairs, he said, is expensive shooting wars, like Vietnam and Korea, which means it's a minor influence this time.
He wonders whether Romney's embrace of more extreme positions in the primaries and his pick of Rep. Paul Ryan for running mate will offset the general impression that he's not as conservative as he says he is. Hansen has been assessing his chances as a relative moderate, especially as he tacks pretty actively back toward the center, including during the first debate.