NEW YORK -- Laurence Luckinbill doesn't bear much resemblance to Lyndon Baines Johnson, really.

He's several years younger than LBJ was when he took to the airwaves in 1968 to announce that he wouldn't seek reelection; he's four inches shorter. Years on Broadway and in Hollywood have purged the native Arkansas twang from Luckinbill's theatrical baritone, while Johnson used to say he had the South in his mouth. Besides, "I'm not that kind of dominant character," Luckinbill points out. "I don't come in and conquer a room."

Moreover, "I disliked him intensely, wanted him out of office, wanted to impeach him." While Johnson was trying to rally the country's support for his Vietnam policies, Luckinbill was defiantly running a SoHo storefront for Gene McCarthy and demonstrating at the gates of the Brooklyn Navy Yard. While he never chanted "Hey, hey LBJ, how many kids did you kill today?" -- feeling that "that wasn't kosher, that wasn't fair" -- Luckinbill arrived at the 1967 Pentagon demonstration carrying a knapsack full of paperbacks of Sen. William Fulbright's cautionary "The Arrogance of Power," placing copies at the feet of nervous National Guardsmen. He regrets this "not a bit."

Yet after 2 1/2 hours of makeup and costuming -- slicked-back wig, foam-rubber jowls and glued-on earlobes, magnificent fake nose, stockman's hat by Stetson -- Luckinbill looks spookily like the 36th president of the United States. More curiously, after months touring with a one-man show called "Lyndon," which last week began previews at off-Broadway's John Houseman Theatre, Luckinbill has grown protective of the man whose fall he welcomed. "Johnson had a vision of a great country," he says. "And people do forget that."

"Lyndon" began life as a public television special, produced in 1987 by David Susskind. The play, adapted by James Prideaux from Merle Miller's "Lyndon: An Oral Biography," begins "seconds after he has gone on television and made that speech" about not seeking another term, Luckinbill says, cradling a cardboard cup of coffee before rehearsal, watching stagehands paint the set. He'll play Johnson for five weeks in New York before heading for Philadelphia and points west.

A veteran probably best known for both the stage and movie versions of "The Boys in the Band" (and for being married to Lucie Arnaz), Luckinbill is onstage for 96 minutes. His meditative Johnson, in a drawl Luckinbill developed with a Texas dialect coach, remembers hitchhiking off to teacher's college, loving the years in Congress and loathing the vice presidency, enduring the shock of Kennedy's assassination, presiding over the anguished endgame during which Vietnam finally eclipsed everything he hoped to achieve.

His body language, as Luckinbill/Johnson moves from his desk in the Oval Office to a podium flanked by American flags to a slump-inducing armchair, comes from the hours the actor spent observing his quarry at New York's Museum of Broadcasting. He watched "press conferences, 'CBS Reports,' news footage ... a whole range of stuff." There was, he observed, "a characteristic Johnson pose": Luckinbill folds his arms, leans forward and glares into his listener's face from six inches away.

It's clear that as the play has traveled the heartland -- Lorain, Ohio; Wausau, Wis.; Aurora, Ill., and all over Texas -- Luckinbill has grown increasingly fascinated by, and tolerant of, Lyndon Johnson.

He's indignant at the first two volumes of Robert Caro's critical biography. Having spoken with a couple hundred people who knew Johnson, "I haven't gotten a personal picture that resembles the driven beast of the Caro books, that venal character," Luckinbill protests.

He's also prone, at the slightest prompting, even without prompting, to launch into a list of Johnson's considerable, and to his mind considerably overlooked, accomplishments. "He passed more domestic bills than any president ... and they were real bills," Luckinbill argues, ticking them off. "The only real gun control law we ever got was in 1968 after Bobby Kennedy was shot. ... The strongest voting rights and civil rights bills we've ever had to this day. Housing. Medicare. Head Start."

Of course, he knew all this as a young actor enamored of the poetry-writing Eugene McCarthy. But mistrust of government in general and hatred of the war in particular tended to color his, and others', perceptions. "I'll tell you how unfair I was, and we were," Luckinbill says. "At first I disliked him just because he wasn't Jack Kennedy."

Luckinbill, always passionate about history and politics and a lifelong Democrat (George Bush is the only Republican ever to get his vote), had intended to become a diplomat. He'd been appointed to the Foreign Service and was headed for language school at the time of Kennedy's assassination, which short-circuited Luckinbill's plans to join the U.S. Information Agency. "I didn't want to work for him," he says of Johnson. "My commitment to serving in government was pretty thin."

At the time, he probably would have qualified as one of the pointy-headed intellectuals that Johnson was always deriding. "But when you listen, as I have, to the Civil Rights Address to the joint houses of Congress maybe 50 times," Luckinbill says, "it's a great American speech, a great presidential speech. It wasn't a cynical speech; it was a staking-it-all speech ... It deserves to be there with the Emancipation Proclamation and Roosevelt's creating the New Deal."

Luckinbill's research -- and "my own maturing," he says -- have made him feel he understands the tortured Johnson more fully. Still, he was extremely nervous last year when "Lyndon" was first performed for an audience that included Lady Bird Johnson.

He'd done "Lyndon" the year before for a World Hunger Year benefit that attracted a number of congressional types to Ford's Theatre in Washington. Lynda Johnson Robb came and paid Luckinbill the "priceless" compliment of saying she wished her children had been there to see his performance. But Lady Bird wasn't in the house.

A year later, though, the president's widow invited him to the Mayflower to perform at an observance of the 25th anniversary of the Voting Rights Act. He selected a 40-minute segment of "Lyndon," got into his makeup and stockman's hat and apprehensively took the stage.

"Afterwards, I came down off the platform, towards her, to exit, and she jumped up and hugged me before I could get offstage," Luckinbill says proudly. "It was totally spontaneous. It was like saying, 'You did okay.' "