This week marks the 15th anniversary of an event that stunned the nation: President Lyndon B. Johnson's announcement on March 31, 1968, that "I shall not seek and will not accept the nomination of my party for another term as president."

Lyndon Johnson had come suddenly to the presidency. He departed it abruptly. The nation had little sense of him as a man. Now, 10 years after his death, there has emerged a growing fascination with his variegated life and personality.

Three books about Lyndon Johnson have made it to the best-seller lists. In the most recent of these books, "The Path to Power," author Robert Caro has delved deeply into the early Johnson years to make a penetrating examination of the origins, motivations and drives of this complex subject. Because the portrait is severe and harsh, some of the late president's former assistants and associates have felt impelled to mount a counterattack, as it were, against the author, raining on him abuse more appropriate for a political adversary.

I cannot join in this. I believe that Robert Caro is not fairly to be judged a jackal. The Lyndon Johnson appearing in Caro's prose is not a fiction. There was such a man. There were many other Lyndon Johnsons as well, but the man's stature requires no protective purging of his past. Told true and full, as it has never been, the story of this remarkable man enhances understanding of his many remarkable accomplishments in a 38-year public career.

A woman who worked loyally in his offices from the House of Representatives to the White House once offered an astute insight. "Mr. Johnson," she observed, "is like a highly bred horse. Handled properly, he can be magnificent, a Man o' War, who can outrun anything else on the track. Mishandled or not handled at all, he can destroy himself in the stall."

I began learning the truth of this only a month after joining his staff. Rep. and Mrs. Johnson invited friends to their home for a Sunday afternoon reception to introduce two new members of his staff, Warren Woodward and myself. At one point, I was talking with two of his closest New Deal allies and friends, Tom Corcoran and Abe Fortas, when Rep. Johnson interrupted. Why, he wanted to know, wouldn't it be a good idea if he introduced legislation to revive the National Youth Administration of the 1930s to ensure jobs for the still-returning veterans of World War II.

Corcoran dismissed the idea with a wave of his hand. "Lyndon, m'boy," he said patiently, "Roosevelt is dead, the New Deal is over, you've got to come into the real world." Fortas readily agreed. The congressman turned on his heel and left the room.

After a few minutes, he returned. I was startled by the abrupt change in his countenance. Lips curled, eyes narrow and flashing fierce anger, he crouched combatively, spewing through clenched teeth a stream of scalding words accusing his two friends of being "traitors to Roosevelt" by "selling out" to business clients to build their law firms. Then, rising to his full height, he jabbed fingers at the faces of both men, shouting, "Which will it be, God or Mammon? You have to choose: God or Mammon?"

There was an embarrassed hush around us. I was stunned and, frankly, appalled. If my new employer's idealism and commitment were admirable, his transgression of the civilities of friendship and social intercourse was, I felt, unacceptable.

Tom Corcoran waited not a moment. He put his glass on the table, went for his coat, kissed Mrs. Johnson at the door, then motioned for me to follow him outside. "Busby," he said, resting a hand on my shoulder, "you've made a good move for yourself. You'll learn more from this man in one year than you could learn from anyone else in Washington in 10 years. But let me give you this advice: Lyndon sometimes gets to be too much. When he does, do what I am doing--walk away. Give him your best, but never let him take your dignity or your integrity."

I followed that advice for three years, then departed. At his insistence, I finally came back to his world, but not to his staff, in 1958. My new relationship was that of a chosen companion, confidante and counselor. With the greater detachment, I devoted myself more to trying to understand where the moods, behavior and habits of the many Lyndon Johnsons originated. One episode with him was revealing.

In 1959, the Saturday Evening Post, then a significant weekly, published a penetrating study by Stewart Alsop of Senate Majority Leader Johnson's legendary powers of persuasion over other men. The article attracted much interest around Washington. Sen. Johnson was puzzled. He did not think his talents were exceptional.

"It is," he told me, "very simple. If you are going to lead men, you go back to the genes and you find out two things about every man in the Senate: did his mother marry beneath herself, and where in his life, what part of it, was the man's father a failure. Once you know these things, then you know what he is spending his whole life trying to make up for and that is what you appeal to in him when you are trying to get his vote in the Senate."

I recognized that he was, of course, speaking of himself. His keen understanding of other men came from a keen, although unadmitted and probably unrealized, understanding of himself. His whole life was spent in a relentless, often tormented, drive to "make up" for his origins and what those origins denied him.

The most embittering denial was education. It was not just that his college education was mediocre. It was that those with good educations must, he seemed to believe, have understandings of a world from which he and his mind were forever excluded. When I first knew him in the House, he frequently asked, obviously hoping that I would agree, "Don't you think five terms in the House are equivalent to a PhD?" He was then serving his fifth term. The quality of his mind approached genius, yet, to him, the absence of academic certification was crippling.

There were other denials. His origins, he knew, had kept him from what he called "the advantages." He was uncomfortable about manners, terrified about situations requiring dreaded "small talk." As late as 1957, he told a new employee, Lloyd Hand, later to be his chief of protocol, that Hand's job was to "go in front of me at parties," handling the social amenities of which he was painfully shy. One came to understand that out of such excruciating insecurities grew the unappealing defenses: arrogance, crudeness, the rude treatment of close friends.

The war with his origins never quieted. When I returned to his world, I lived in Austin and often was with him at his ranch. At the end of the day, I would ride with him as he drove over his acreage, musing about affairs in Washington. On infrequent occasion, something would impel him to head into Johnson City, where he went through a poignant ritual that seldom varied.

Driving his Lincoln Continental, he would turn off the highway and circle the block on which stood his boyhood home. Then he would cross the highway and, falling silent, drive slowly past one block of small stores and caf,es where, every afternoon, a row of weathered men in coveralls squatted on the sidewalk, idling away their hours and their lives. He knew most of them, they all knew him, but there was never a wave, greeting or acknowledgment between them.

At the stop, before entering the highway again, he would raise his hand toward me, positioning thumb and forefinger about an inch apart, leaving unspoken the words that, I knew, explained the gesture. Considering his origins, he was saying, he had come that close--the distance between thumb and finger--to spending his life as one of those men on the sidewalk.

On the morning after his election in 1964, the largest popular-vote victory ever, I flew to the ranch at his request. I was not surprised when, within a few days, he turned the Continental one afternoon toward Johnson City, and I accompanied him, for the last time, on his private pilgrimage. It ended with the same silent gesture.

There were many Lyndon Johnsons. Some were admirable, brilliant, even, on occasion, awesome. Others were deplorable and detestable, small, abusive, unworthy of his high stations. To acknowledge this is not an act of disloyalty; it is only an act of honesty.

In 1971, at the dedication of the library in Austin that contains the archives of his long career, Lyndon Johnson read over the speech prepared for him, approved the passages exhorting scholars and authors to make full use of its contents to tell his story, then asked for a pen. He added to the text three words: "warts and all." I would hope that all who served him will stand aside to let his remarkable story be told, as he would want it, "warts and all."