THE LONG TITLE of this latest book on Lyndon Johnson is only a partial explanation of what lies ahead for the reader. The Politician is in part a new biography of a man whose life continues to fascinate and disturb many Americans. But it is much more than that, and the ambition Ronnie Dugger, the respected publisher of the Texas Observer, brings to the work is perhaps its greatest weakness.

He writes, "This work is my attempt to understand in the life and times of Johnson, what (C. Wright) Mills called 'the history of the present.' More narrowly stated, the subject before us is Lyndon Johnson and his heritage as it was delivered through his career and presidency into the life of the world." In other words, this is Dugger's view of today's world as revealed through a partial retelling of the life of Lyndon Johnson.

It is hard to imagine undertaking a biography of Johnson and then concluding that this is the narrow purpose of the book, but somehow Dugger has attempted to do it. The result is a book whose chronological ending is Johnson's election as Senate Democratic leader in 1953, but which espouses Dugger's theories on everything from why Johnson led America into Vietnam to the role Johnson will have played in causing World War IV. Some of it is provocative and controversial, as Dugger clearly intended. Some of it is merely frustrating.

Dugger stretches the reader's credulity. In the beginning, apparently to justify the sweep of the book, he redefines history. The last 50 years, he asserts, are best understood in political terms not as the Roosevelt era but the Johnson era. Later, he says that McCarthyism ran from 1947 to the end of the Nixon presidency, although it was practiced in Texas for 15 years before it went national. World War III, he writes, has been in progress since virtually the end of World War II, which is why the next war is going to be World War IV. And, says Dugger, "If the holocaust comes and if there is still a human history, the global American hawkery of the Johnson Period will be understood as a principal cause" of it.

If there is an underlying theme, it is the threat of nuclear holocaust and how the Johnson years made the danger of annihilation possible. That focus may make this book timely, given the recent national interest in a freeze on nuclear weapons. But in reality, The Politician is awkward and unsatisfying both as biography and polemic.

For more than three decades, Dugger's Texas Observer has been the liberal voice in conservative Texas. It has fought relentlessly against the collusion of economic and political interests that often have governed at the expense of the people, and Dugger has brought this uncompromising viewpoint to his treatment of the man who loomed over Texas politics for a generation.

Dugger also brings a unique regional eye to Johnson. He describes Johnson as a man deeply influenced by the often mythical heritage of the western frontier and argues that Vietnam was caused in part by the Alamo, which meant more to Johnson than Bunker Hill does to most other Americans, and that Johnson fought the Communists in Indochina the way his ancestors ravaged the Indians on the frontier. "His foreign policy killed Communists while building schools and hospitals and civilizing the friendly natives," Dugger writes. The traditions of the frontier--courage, honor, manhood, revenge--were so deeply imbedded in Johnson from childhood that he knew of no other way to approach the conflict in Southeast Asia than to attempt to destroy his adversaries.

There are some richly detailed chapters in this book-- on Johnson's stolen, 87-vote victory in the 1948 Senate race, on how Johnson won the Silver Star from Gen. Douglas MacArthur while on an inspection mission in the Pacific in the early days of World War II, on LBJ's connection with the antiunion construction empire of Brown & Root Inc.

But along the way, there are jolting digressions to explain the historical significance of Franklin Roosevelt, Teddy Roosevelt and Harry Truman, Richard Nixon's opinions on World War III, and rapier jabs at the bellicosity of Ronald Reagan.

The Johnson who emerges here is two dimensional, a spineless politican who bent with the political winds, who followed the New Deal just long enough to get elected to Congress as a protege of FDR and then turned against it to seek higher office in Texas, who shamelessly courted his more powerful elders at whatever cost to his convictions, who was a redbaiter before McCarthy and a union hater because his friends Herman and George Brown of Brown & Root supplied him with campaign money. He taunted the Russians, eagerly sought a confrontation with them and warned America that it was foolish to assume it could avoid a final conflict with the Communists.

Much of that is literally true, but there is only a little sense from Dugger of the context of the times, the force of energy Johnson brought to his work, the cunning sense of people that helped him master the Senate, the power he had to motivate others, the desire he had to help poor people, the sheer humanness of the man or the complexity of his personality that is revealed in earlier books by Doris Kearns and Merle Miller. Dugger's Johnson is an unprincipled hawk, a Strangelovian "Senator from the Pentagon." How did this man rise as far as he did?

Given the long gestation period of this book, there seems little doubt that Dugger's publisher wanted to get it into print before the first volume of Robert Caro's massive--and, based on the excerpts that have appeared so far, compelling--biography appears next fall.

But most of what Dugger really wants to say about Lyndon Johnson is contained in the chapters that break the biographical chronology. It is a shame that in the rush to publish, he was not able to jettison much of what he had gathered over nearly two decades of research in favor of a straightforward, interpretive history of the Johnson years. That could have been just as provocative as The Politician, without the irritations.