The Final Debate Drunkblog Before the Voting Begins
So there's a routine at these debates.
At the start, the moderators remind the audience against any unruly outbursts of support. But then the candidates get people so worked up over a vital issue, that they just can't help themselves and burst into applause. Then the moderators warn them again, and then it happens again anyway.
That hasn't happened tonight, except for the initial warning.
I'm reminded of the old Steve Martin gag (from "Grandmother's Song") about getting all exciting and going to a yawning festival.