Gail Shister
TVNewser Columnist

Hold your applause, says Charlie Gibson.

Unlike some moderators, ABC's Gibson won't tolerate hand-clapping from the studio audience during a presidential debate. No exceptions.

"These things are very serious business, and applause doesn't lend itself to the dignity of the event, in my mind," says Gibson. "I don't think it belongs there. It's distracting to the people at home as well as to the candidates themselves.

"Subconsciously, it gets in your mind, and it can color the way people see the debate. The audience is supposed to be an observer, not a participant."

ABC political director David Chalian agrees. "These candidates go to rallies all the time. They are applauded constantly...Otherwise, it eats into [their] time, and breaks the rhythm."

Gibson and 'This Week's' George Stephanopoulos will moderate the Hillary Clinton-Barack Obama debate at the National Constitution Center in Philadelphia at 8pmET April 16 — six days before the crucial Pennsylvania Democratic primary.

It will be Gibson's third debate this primary cycle. In an unprecedented feat, he anchored back-to-back events (six Republican candidates, followed by four Dems) on Jan. 5 in Manchester, N.H.

Compared to that marathon, prepping for next week's verbal wrestling match is a trip to the beach for Gibson.

"I obsessed about it [New Hampshire] for weeks," he says. "I had never done anything like it. I kept thinking there was no way to prepare enough for it. I sort of went into a closet by myself. This time, I've got George. He knows this stuff backwards and forwards."

As with New Hampshire, there will be no strictly enforced time limits on candidates' responses in Philly, Gibson says. If someone starts to filibuster, however, he will jump in.

In a new wrinkle, ABC is taping questions from numerous Super Delegates, since "they might be the ones who decide this election," Gibson says. No decision if any will be used during the 90-minute debate.

If, by some chance, Clinton or Obama says something amusing April 16, Gibson says titters from the audience are acceptable.

"I don't want them sitting on their hands. If somebody says something funny, they can laugh."

Clinton or Obama funny? Now that's debatable.