When the part of Richard M. Nixon in the play "Secret Honor" was offered to actor Philip Baker Hall, he was not interested. Really not interested.

"One, I didn't like Richard Nixon and had no interest in a play about him," said Hall, a compact man of 54 who bears no resemblance to the former president. "Two, the script was about two hours and 20 minutes long and not as good as it is now. And three, I had no idea how to work on it."

Only after several months, when Hall had read and reread the one-character play, did the idea of a particular speech pattern come to him as the "stylistic key" to the part -- a stammering, forced kind of speech that generates tension apart from the scathing substance of the script. When that (number three) fell into place, his problems with number two and number one diminished. "I could see it would be a big hit," he said.

And indeed it has been a hit of sorts, albeit on a fairly esoteric level. Film producer Robert Altman saw the original Los Angeles production and decided immediately -- that very night -- to underwrite a New York production and a movie version. Hall, now performing "Secret Honor" at the New Playwright's Theater, has been acclaimed for both stage and screen portrayals, nominated for awards in New York and Los Angeles and won the Best Actor award at the Capetown, South Africa, Film Festival.

The part is a tour de force, two hours of an imagined Nixon, alone and ranting. He talks to the portraits of Dwight Eisenhower, Woodrow Wilson and Henry Kissinger, spewing profanity and bitterness, claiming that he resigned rather than face charges of treason that would bring down the Republic.

For Hall, the performance is an endurance test. He lost 35 pounds during the first run and has regained only about half of it. He cannot quote a line from the play out of context; for him, "It's one long sentence."

"The commitment has to be so total," he said recently. "Every night before I go on I wish I were somewhere else . . . It requires that I become this wacko for a couple of hours, which is not really my nature."

Hall was determined not to do an imitation of Nixon -- "no 'Saturday Night Live' images" -- and indeed his portrayal summons forth ghostly memories without making you feel caught in some television time warp. "I don't feel I'm doing Nixon," he said. "It's a fictional character who has sold his soul to the devil and wants to get it back without giving up what he's got."

Playwright Donald Freed collaborated on the play with lawyer Arnold Stone, a one-time Justice Department attorney who supervised federal investigations into organized crime. Stone is also a Nixon buff, and between the two of them they surveyed more than 100 books about Nixon and Watergate, including documents previously released under the Freedom of Information Act. The play, however, is subtitled "A Political Myth," lest anyone be confused that it bears any resemblance to real life.

Freed, a self-described anarchist and radical, denies Stone's main function was to prevent them from being sued, but concedes that his name as coauthor "stops certain people from saying [the play] is just a Marxist spy story."

Freed recently settled out of court a multimillion-dollar lawsuit against him filed by an organization of former CIA agents who claimed his novel "Spy Master" and his book "Death in Washington" defamed intelligence officers. Freed said that although an early ruling by a federal judge in the matter was in his favor, he could not afford to continue his legal defense and so agreed to print a retraction in Publisher's Weekly in return for the suit being dropped.

No one has tried to sue him over "Secret Honor," however, although Hall said several performances have been attended by suspicious-looking men in dark business suits -- the type not usually seen in the small offbeat theaters in which the play has been produced. Their reactions to the performance were conspicuously muted.

"I believe that Nixon has seen a tape of the movie," said Freed. "But he hasn't written to tell me what he thought."

Freed's next play should continue his reputation for controversy. s Called "Circe & Bravo," it's about a first lady and her relationship with a Secret Service agent. It is scheduled to open soon in London, with Faye Dunaway starring and Harold Pinter directing. "It's too hot to open in this country first," said Freed.

Hall, although no fan of Nixon, is motivated more by the great part rather than any political leanings. After 25 years as an actor, he has played more than 130 leading roles in theaters around the country, moving from New York to Los Angeles because "in 1961 there were 300 plays produced in New York, and in 1975, when I left, there were 39."

His deep, husky voice, made more so by endless cigarettes, may be his most distinctive feature, one he had even as a child in Toledo. He has a slightly woeful air and is given to gloomy asides -- such as calling playwrights' workshops in which he and other Los Angeles actors participate "an effort to keep the theater alive -- which will probably die despite all our efforts."

A friend, who makes $500,000 a year doing voice-overs for commercials compared with Hall's $400-$600 a week take in the theater, recently told him it was time Hall got off his artistic high horse and started selling his distinctive voice.

"He said, 'That voice will not always be there, you got to get out of this theater thing.' " So Hall signed on with the leading voice-over agency.

Twice divorced, Hall has two adult daughters, one of whom is training to be a drama critic. He recently bought his first house -- having lived in rented apartments his entire life except for one year -- and is employing his skills as a furniture designer and carpenter to renovate it.

Just before the Washington run of "Secret Honor" (which has been extended to Feb. 16), Hall played a "paranoid, brutal Russian tank commander" in "Nanawatai," William Mastrosimone's play about the Russian invasion of Afghanistan, which opened the new Los Angeles Theater Center. He was also in the center's third production, a revival of "The Petrified Forest," in which he played Duke Mantee opposite Rene Auberjonois.

"Mantee is on stage the whole second act but he only has 25 or 30 lines," Hall said. "I haven't played another role that required so little and gave so much back in terms of response. It was great to do a part in which I didn't have to kill myself. And then I agreed to do this Nixon again!"

Hall says after this he is absolutely through with Nixon -- unless productions are mounted in either London or San Francisco. In that case, well, "I don't think I could let someone else do it."