What do you remember from the debates four years ago? Probably not the candidates' positions on missile defense, but how about Al Gore's sigh or the look on George Bush's face when Al Gore came at him across the stage, or the first President Bush looking at his watch in 1992 as though he couldn't wait for the debate to be over?

Way back in 1960 in the very first modern debate, radio listeners thought Richard Nixon made a better case than John F. Kennedy, but TV viewers saw Nixon's sweaty upper lip and five-o'clock shadow and they called the relaxed Kennedy the winner. It's things like these that make the debates memorable and dangerous.

David Gergen says, "The importance of the debate all depends on how close the race is. Very close race, the debates can be decisive."

Sometimes, just a good line or two does more for a candidate than an hour's worth of speeches.

Ronald Reagan, with decades of acting and speaking experience, may have been the best at seizing the moment. In 1984, he neutralized the age issue against the much-younger Walter Mondale.

"I am not going to exploit, for political purposes, my opponent's youth and inexperience."

Bill Plante says, “Televised debates were supposed to give the candidates a national forum to talk about the issues, but in the format candidates want, which isn't really a debate, they've become political reality TV, personality contests and fair game for late-night comedians.”

"On track, stay the course, 1,000 points of light, and stay the course. I can't believe I’m losing to this guy."

Watch Thursday night for the unscripted and unguarded moments. They're the ones you're likely to remember.