But a much different, less valiant picture of Thompson emerges from listening to the White House audiotapes made at the time, as President Nixon plotted strategy with his aides in the Oval Office.
Thompson's job on the Watergate committee was to lead the Republican side of the investigation. He was appointed by his mentor, Sen. Howard Baker of Tennessee, who is now co-chair of Thompson's 2008 presidential bid.
When Nixon's aide H.R. Haldeman told Nixon of Thompson's appointment, Nixon was less than impressed.
"Baker has appointed Fred Thompson as minority counsel," Haldeman is heard saying on one tape.
"Oh sh--, that kid," Nixon responds.
"I guess so," Haldeman replies.
Nixon worried that Thompson's Democratic counterpart, Sam Dash, would outsmart Thompson.
"Well, Dash is too smart for that kid," Nixon says on another tape from March 16, 1973. The existence of the tapes were publicly revealed by a question from Thompson at a Watergate hearing and led to the president's resignation. They are preserved at the National Archives in College Park, Md.
"Sure. Runs circles around him," agrees an aide, John Dean.THE BLOTTER RECOMMENDS
As the investigation picked up speed, Nixon grew increasingly concerned about whether Thompson could stand up to the Democrats.
In this May 1973 recording, he shared his concern with then-chief of staff Alexander Haig.
"He's talking to Fred Thompson. I said you're not --," Haig begins.
"Oh sh--, he's dumb as hell. Fred Thompson," Nixon interjects. "Who is he? He won't say anything."
In another conversation some weeks later, Nixon and his advisers were still describing Thompson as not very smart but at least beginning to play ball.
"Our approach is now, we've got a pretty good rapport with Fred Thompson. He came through fine for us this morning," White House counsel Fred Buzhardt says on a tape from June 6.
"He isn't very smart, is he?" Nixon asks.
"Not extremely so, but --," Buzhardt says, interrupted by the president.
"But he's friendly," Nixon says.
"But he's, he's friendly," Buzhardt echoes.
A few days later, White House aides are heard saying Thompson will be even more helpful than his boss, Sen. Baker, and that Thompson agreed to secretly help undercut the credibility of White House whistleblower John Dean.
"They've finally got [Dean] under oath," Buzhardt says on a tape from June 11. "Uh, Thompson will work with us. So, good."
"Does he realize that Dean has some problems?" Nixon asks.
"Oh, yes sir," Buhardt responds. "Quite a few...He is willing to work with us; he is also now willing to work with us on shifting some focus to the Democrats. He's finally made up his mind; he's got to start looking at some of their stuff."
Later in the tape, Buzhardt says, "[Thompson is] willing to go, you know, pretty much the distance now. And he said he realized his responsibility was going to have to be as a Republican increasingly."
In his memoir of the Watergate era, Thompson admits to secretly alerting the White House to key evidence as it was discovered by congressional investigators.
Former Watergate committee investigator Scott Armstrong told ABC News that Thompson's cooperation with the White House undermined the investigation.
"It was the equivalent of two prosecutors knowing about something and one of them going behind the scenes and telling the person being accused what the witnesses were saying about him," Armstrong said.
Two months after Buzhardt's comments, Nixon resigned. Thompson would later take credit for helping to reveal the secret White House taping system that led to Nixon's downfall.