With John Daniel Reaves.

THE KINGFISH! Book by Larry L. King and Ben Z. Grant. Set designed by Rhonas A. McGee and Cheryl K. McGotrick; lighting by Tomm Tomlinson; sound by Jacky English; costumes by John Daniel Reaves; produced by Barbara S. Blaine.

With the triumph of "The Best Little Whorehouse in Texas," writer Larry L. King established himself as the leading chronicler of his native state and its mores -- if that is the right word in this case. Now he has done the same for neighboring Louisiana in "The Kingfish!", which officially opened last night at the New Playwright's Theater.

This one-man play is described by King and co-author Ben Z. Grant as "loosely depicting" the life and times of populist demagogue Huey P. Long.

The subject himself was, in effect, on stage for most of his adult life as governor and senator. So the challenge for actor John Daniel Reaves is to live up to the Kingfish's Thespian model on countless -- often literal -- stumps during the roughly two decades between his guileful start in Louisiana politics and the day when an assassin cut him down before Long could deliver on his threat to the presidency of Franklin Roosevelt.

Few in the audience are old enough to know whether Reaves is taller or shorter that Long, his voice higher or lower, But the familiar qualities are all there -- shamelessness, vanity, feistiness, self assurance, megalomania, deviousness and a razor-sharp mind.

Reaves, a Washington lawyer who studied drama at Auburn and has played Beckett and Dylan Thomas at various theaters, portrays a very plausible Long in passages such as this one near the end, when he declares of his fellow U.S. senators: "I don't give a damn about what my colleagues think. I know they hate me. And why not? I hate them."

It was such cut-throat aggression, combined with Kingfish's extraordinary magnetism before a crowd, that made FDR consider him potentially the toughest foe he ever might face.

Yet in one-man shows, character alone is not enough. Often the very popular progenitors of "The Kingfish!" -- recounting the stage and platform lives of Dickens, Twain, Will Rogers, Harry Truman and others -- seemed tedious to some observers. They consisted of fragments -- even one-liners -- that were short on cohesion and failed to build toward dramatic climaxes.

But here King and Grant have produced a script that ingeniously avoids both problems. The dramatic line is a natural chronology, in which Long returns to address a 1979 audience in his 1930ish double-breasted white linen suit, white shoes and a straw boater.

He confidently declares that the only speakers since his time to match him are "Kennedy and the Rev. Dr. Martin Luther King Jr." He also compares himself to Jesus Christ and Churchill.

The Kingfish recalls his life from the beginning in dirt-poor Win Parish, near the Arkansas border. Even though only one person is on stage, the narrative dwells mostly on extended exchanges with other persons, with Reaves repeating enough of what the other person says, and asking enough questions so that the illusion of separate scenes develops. They range from discussions with other legislators who are trying to impeach him as governor to an audience with FDR that opens with Long saying, "Mr. President, I hear you consider General Douglas MacArthur and myself to be the most dangerous men in America. And I certainly agree with you about him."

To tie the hour-and-three-quarters show into this kind of dramatic development, authors King and Grant have had to bend the details of Long's life. They declare in the program that they "have attempted to keep their vehicle within the historic fence-rows." The climax, of course, is the assassination as Long walks in the halls of the Baton Rouge statehouse ("the people's palace") that he built.

This is wisely understated. The shots at Long -- and the ensuing barrage of bullets from his bodyguards, who mowed down the assassin -- are played by tape to a relatively dark theater. They are followed by a voice over in which Long talks to his nurses as he is dying.

Not everyone will buy King's view of Long as an endearing "scalawag," among other things. Some will agree with Walter Lippman, who in 1935 wrote: "The dictatorship of Senator Long presents a question of principle about which there is a dangerous confusion in the minds of many who believe in democracy. The question is whether men must acquiesce in the overthrow of democracy if a dictator could obtain the support of a majority of the voters."

The show, produced by King's wife, attorney Barbara Blaine, runs through Sept. 9.