'Lyndon:' Klugman's salty one-man show

''You tell the Washington Post, if I decide to run, they'll be the last to know,'' he drawls into the phone and slams it down as the curtain rises on ''Lyndon.''

Up there on stage, striding around in Lyndon Baines Johnson's cowboy boots, is street-smart, urban Jack Klugman of TV'S ''Quincy'' and ''The Odd Couple.'' Klugman as LBJ turns out to be a real urban cowboy who bravely rides out this bucking bronco of a role and is never thrown, although his style may raise a few eyebrows.

He manages to create an LBJ aura on stage, to create an LBJ impression, to bring back an era, in spite of the fact that Klugman is obviously no Johnson clone.

Unlike Donald Moffet, who closely resembled LBJ in ''The Right Stuff,'' Klugman is not typecast; he is not a tall, rangy Texan with a cottonwood drawl. But he's reportedly done vast amounts of research, studied hours of LBJ clips and tapes, read the LBJ biographies from Robert Caro to Merle Miller's oral biography of Johnson, and come up with a nostalgic variation on the LBJ theme audiences appreciate.

But it is not an uncanny re-creation of the character, as Hal Halbrook did with his one-man show on Mark Twain or Julie Harris with Emily Dickinson in ''The Belle of Amherst.'' Although Klugman struggles valiantly with Johnson's twangy drawl, it sometimes gets the better of him. It's as though he'd taken a Berlitz course in Texan and left before the last lesson.

He catches moments, too, that are Lyndonesque, like the occasional foxy grandpa look over his glasses as he scores a political coup. In his blue suit, boots, red and blue striped tie, and white shirt, the silver-haired Klugman looks and sounds, at a distance, like LBJ; but he could never be taken for LBJ at close range.

Still, in Washington where politics is the salt and pepper of life, ''Lyndon'' has a sure audience. Klugman received a standing ovation after his grueling 90 minutes on stage, from a full house that appreciated every political nuance. ''I'm the only president you got,'' he keeps reminding six of the nation's most powerful men from his phones in the Oval Office, and the audience loves it.

James Prideaux's superb script, inspired in part by the Merle Miller taped conversations, is the keystone of this one-man show which is directed with snap and panache by George Schaefer.

''Lyndon'' shows us the bigger-than-life, occasionally crude, tougher-than-tensile-steel Texan who gulped down power like cold sodas on a hot day, waffled over, then fought for civil rights, and hammered home the Great Society benefits.

It also shows the tragic LBJ who waded into the swamp of the Vietnam war, which swallowed up his presidency and forced him not to run again. ''I'm all slicked down with tarnish,'' he mourns at the end. ''Lyndon'' is an ideal show for Washington, where it doesn't matter whether the administration is Republican or Democrat.

Politics is always center stage. Whether it's boffo enough for Broadway, laid back enough for Los Angeles, or, in a previous administration's words, whether it will play in Peoria is debatable.

''Lyndon'' will be at the Shubert Theatre in Philadelphia through Feb. 26; then Boston's Wilbur Theatre from Feb. 28 to March 11.