You know you've seen that mug somewhere before as it looms several feet high on the movie screen. The brooding eyes under heavy brows, the full lips contemptuously curled as he badgers the witness. Obviously some character actor, but what's his name? Then the credits role: Fred Thompson, played by "Himself."

"Himself" looks familiar because he is familiar. As minority counsel to the Senate select committee on Watergate, Fred Thompson came into living rooms across the nation via TV, along with lawyer Sam Dash, senators Howard Baker, Sam Ervin and an unforgettable supporting cast. In reel life, Thompson plays Sissy Spacek's lawyer in "Marie: A True Story." In real life, Thompson, who went back to Tennessee to practice law following Watergate, successfully defended Marie Ragghianti, a young political appointee, against unlawful dismissal by then-Tennessee governor Ray Blanton. The successful trial triggered an investigation that ended up with Blanton and aides in jail, led to a book about Marie and now the movie.

Although the movie is generally panned as a saintly snore about a good woman who discovers that clemencies and pardons are for sale, battles the bad guys and wins, Thompson gets raves. One recent day in his Washington law office, Thompson savored his reviews: "His sly, muted performance makes the familiar courtroom scene fresh and new." . . . "A natural star, he gives so much oompf to the courtroom scene it almost makes you want to commit a crime just to hire the guy." And more. Then Thompson's booming laugh shakes his 6-foot-5 3/4 hulk as he reads aloud one zinger: "Fred Thompson plays himself . . . with a self-congratulatory zeal that would make Muhammad Ali blush . . . simply insufferable."

Cynics don't have to be convinced that lawyers are actors, but the surprise is that Thompson does it so well. He enjoys a frequent look-alike comparison with Joe Don Baker. "Back during the Watergate stuff I had a girl come up to me and ask for my autograph." A derisive smile pokes fun at his own ego. "In those days I carried half a dozen pens with me just in case somebody would ask. I gallantly whipped one out and I got halfway through when she said, 'I certainly did enjoy you in 'Walking Tall.' "

Now 43, fleshier than in Watergate days, losing more hair, Thompson says he'll never leave law but would love movie moonlighting. In fact, he seems to like nothing more than talking about his new career -- agents proffer everything from movie scripts to commercials -- as he rocks back and forth in an overstuffed leather chair, tamping his pipe and looking for all the world like the laconic good-old-boy lawyer of "Marie."

"Talk about a low budget movie! The boots were mine. The clothes were mine. I tried on one suit that wardrobe gave me and sent it back. The 10-gallon hat I've had for years."

And in most instances, the words were his.

"So much of the trial scenes were verbatim. Everybody says 'You weren't acting, you were just playing yourself.' " Outside the courtroom, Thompson improvised often. In one scene he picks up Spacek, who has been brought in on a trumped-up drunken driving charge. "The original dialogue had me coming in and seeing her sitting there and saying 'a fine client you are.' I told Roger [director Roger "Smash Palace" Donaldson] that I wouldn't say that. So they said 'Well, what would you say?' And I said that I'd probably say something like 'Come here often?' Roger said, 'That's good, we'll use that.'

"It sounds like walking and chewing gum at the same time, but honest to God the toughest part for me was walking, hitting your mark, saying your line, turning, hitting another mark, saying another line and walking out the door. Now that is tough for a lumbering kind of guy who doesn't pay much attention to that."

Some real-life Tennessee journalists have cameo roles, but Thompson is the only amateur with a major part and dominates the climactic courtroom scene. He was not intimidated playing with Oscar-winning Spacek ("she made you feel like you'd known her like the girl next door 30 minutes after meeting her").

Although there are a couple of murders and a rape, the movie seems curiously unengaged until the trial. Thompson, who has seen the movie half a dozen times, faults it for not "accurately portraying the fact that Marie made such an impression on the witness stand. I went into her training, honors she had gotten, etc. By the time she left that witness stand, if that jury ever thought she was some floozy who slept her way to the top, they knew better. I think that, more than anything, won the lawsuit."

Thompson at first spent a lot of time trying to talk his client out of a lawsuit against a sitting governor. "And then I looked at the accusations and inferences and the stuff they were spreading about her, and knowing the real reason they got rid of her was to cover their tracks. That overkill is the only reason I took the case. It's because of that overkill that we're having this interview."

Getting the part took some time. "We kinda did a little toe dance around each other for a while." Finally Thompson read for casting director Lynn Stalmaster who then asked if he could go to New York to read for producer Frank Capra Jr. and Donaldson. "And I said [drawl] 'I might could work it into my schedule.' " Thompson likes his shtick as he grins and adds, " 'Couldn't possibly come up before tonaaght.' " When Dino De Laurentiis saw the screening, he shouted "Blanton!," thinking Thompson would be perfect for the villain.

Thompson's charmed life, as he terms it, was hardly predictable. "My mother and dad never got past the eighth grade. My dad's a car salesman in the little old town where I grew up [Lawrenceburg, Tenn., population 12,000]. I had the best kind of background. Dad wasn't a leading lawyer I had to try to measure up to. On the other hand, because they had little education, they were totally proud of me. When I got my high school diploma they were proud of me."

And with good reason. He chuckles. "I barely got out of high school. I was interested in two things -- and sports was one of them. I was voted most athletic in my class in my junior year. The teachers got together and decided that anyone with the number of demerits I had -- not to mention my overall grade-point average -- should not be a superlative at Lawrence County High. And they took it away from me and had a new election."

Thompson "had sports aspirations but I dislocated my shoulder, got it absolutely torn up, and got married in the same week. Talk about changing a boy's perspective on things." After a lengthy separation, Thompson and his high school sweetheart, the mother of their three children, divorced earlier this year.

As a young father, it was a tough slog through Memphis State University and Vanderbilt University Law School. Then, as a federal prosecutor, Thompson had his share of bank robbery and moonshine prosecutions. "My old granddaddy is probably turning over in his grave about my prosecuting moonshiners. I don't know directly but I have my suspicions about him when he was a young man."

A friend talked Thompson into running Howard Baker's 1972 Senate campaign. "Talk about life going full circle. That young man is now Gov. Lamar Alexander, who took over when Blanton was ousted early."

In 1973, Thompson's life changed forever when his mentor Baker named him minority counsel to the Watergate committee.

Critics call Thompson a Republican gun for hire. In addition to Watergate, Thompson was special counsel to the Republican-run Senate Foreign Relations Committee for Alexander Haig's confirmation hearings and counsel for the Senate Select Committee on Intelligence for the probe of CIA Director William J. Casey's financial investments. The panel was critical of Casey for withholding information from the committee, but found him "not unfit" to serve his post.

Thompson shrugs at criticism that he was too much a Republican advocate. "Sure people are always going to say stuff about Republican partisanship -- 'it's like the fox guarding the henhouse.' So let 'em. I think too much of myself to do that."

As for Watergate, Thompson says, if he had it to do over again, "I would be more of an advocate instead of less. If you had a Republican-controlled Senate investigating a Democratic administration I would feel it incumbent on that minority counsel to make sure Democratic officials got a fair shake." Thompson still complains that the Democrats tried, among other things, to "set up" then-Nixon speechwriter Pat Buchanan. "They told him they had given him all the documents they were going to question him on. I found out they didn't and I called Pat at home that night and told him what was coming. And he ate 'em alive the next day. I fault myself for not being aggressive enough from time to time because of the overwhelming press sentiment." As an unseasoned 30-year-old, says Thompson, "in my heart of hearts I knew the criticism I would receive if I was any tougher than I was."

He also "had to be dragged kicking and screaming into reality on some of this stuff." He shakes his head remembering his first reaction to Alexander Butterfield's bombshell that Nixon had taped White House conversations -- tapes that ultimately brought the president down: "It had occurred to me those tapes would still not be around over there if they hurt the president and maybe he had sent Butterfield over there to disclose that. Nixon, the wily old fox that he was, maybe arranged the whole thing."

Today Thompson divides his time between Nashville and Washington where he lobbies for, among others, Westinghouse, cable television and the Teamster's Central State Pension Fund. "They were allegedly the bankroll for the mob, to put it in delicate terms. But it has been cleaned up and [former Democratic senator] John Culver and I serve as their Washington counsel. Anyone will tell you it is now a model fund."

Thompson toyed with running for Baker's Senate seat but decided that elected office is not worth it; "the hassle factor is up and the pay is not." He plans to help Baker in his expected 1988 presidential race.

He is also trying to write a novel. "It has to do with lawyers and politicians and the mine fields a young lawyer encounters. A personal thing as to the choices one makes and the dichotomy so many of us have to live by in balancing our ideals. Not running over the other guy on one hand and on the other, the pressure that society brings on us where we're measured in terms of our income, of who we're able to do in, and the pressures of a big law firm. And how the good guys turn out not to be so good and the bad guys turn out not to be so bad."

Where does he put himself in the good-guy / bad-guy category?

"Myself? Ohhhhhhh. Gosh. Gee." Pause. "I think I'm a pretty good guy -- with certain bad-guy characteristics. Like failing to keep in mind what's important and not important."

Thompson admits to being dazzled by some of the glitter, and says, "Up here, it's a town on the make. Everybody is here for a purpose. And I'm a part of that. But I need the distance and variety.

"I need to go down to general session's court in Lawrence County once in a while and sit around and whittle and chew a little tobacco with the ones who knew me when I was a kid."

Then Thompson, not wanting this conversation to get too all-fired serious, mind you, and wanting to add a little roguish sincerity to it all, laughs his booming laugh.

"Now I'm not going to go down unless I get paid for it."