Who won Wednesday evening's Intelligence Squared debate and why.

But Bergen's moment wasn't enough.

The final score was 46 percent for the motion, 43 against and 11 undecided. Hayden and Falkenrath "won" because they attracted more new supporters—an additional 15 percent—with their argument.

John Donvan, who has presided as a moderator for 33 of 51 Intelligence Squared U.S. debates, * says Falkenrath and Hayden won because their argument was more clear and unified. They also "had an ability to pick part the differences between Juliette and Peter's two arguments."

Hayden's closing statement reflected Donvan's analysis, pointing out that Bergen and Kayyem were making separate points. "From Peter I think I'm getting the argument that 'you've been successful, back off, you've won the thing,' " he said. "And from Juliette I'm getting the argument 'You shouldn't have been doing all those things that you were doing that Peter said were successful.' "

Still, despite the loss, a relaxed Kayyem said she was happy with the outcome of the debate and struck by the audience's perspectives. "The final poll numbers show that we are a nation still struggling about what the conception ought to be of how we fight this," she noted. "What was interesting about that was how many undecideds there were coming in," she noted. "And maybe that's good. Maybe this nation is more open to things than I thought."

Correction, Sept. 8, 2011: The article originally repeated John Donvan's account, at the event, of having moderated 35 Intelligence Squared U.S. debates. In fact, he has moderated 33. (Return to the corrected sentence.)