Robert Caro, now 76, had his epiphany on power when he was sent as a young reporter for Long Island Newsday to cover a plan by Robert Moses to build a bridge from Rye, N.Y., across Long Island Sound to Oyster Bay. It was, he recalls, the “world’s worst idea,” and he wrote a series exposing the folly of the scheme. He convinced everyone, it seems, including New York’s Gov. Nelson Rockefeller; but the State Legislature approved the plan 138 to 4. In 1964 Caro concluded that bridges and highways are built not because of scientific studies but because Robert Moses has power and puts them where he wants. So Caro wrote The Power Broker (1974), the 1,200-page saga of how one city planner’s ego, implanted in the Triboro Bridge and Tunnel Authority, transformed the face of New York and Long Island, fed by the urban-auto myth that every upwardly-mobile citizen would have two homes—one in Manhattan for work and the other on Long Island to nourish the spirit.

The impact of the book set the stage for a five-volume biography of Lyndon B. Johnson, of which this is the fourth. Of Caro’s five books, three have the word power in the title. This one is no mere biography of an individual but a profound analysis of Lord Acton’s 1887 maxim: power corrupts. Critics have labeled Caro’s opus Shakespearean; it fits the classic theme of tragedy where the ego-blindness of a potentially good leader, deaf to the voices of prophets, brings a whole world to ruin.

The Passage of Power covers only six years, starting in 1958 when Senator Lyndon Johnson is ambivalent about pursuing the Democratic nomination for president but shys away because he fears the humiliation of losing. This hesitant soul is the same 13-year-old boy who, when a group of children sat at recess under a hackberry tree, looked at the sky and, driven by his father’s financial failure, proclaimed: “Someday I’m going to be president of the United States.” The narrative moves inexorably to Dallas, then to the determination of a dramatically transformed Johnson to establish his credibility by fulfilling both John F. Kennedy’s legislative program and his own compassionate vision for social and racial justice.

The sick heart of the narrative, however, is the crippling hatred between Johnson and Robert F. Kennedy. And as the story develops, Caro turns back the clock to fill in the biographies of the stars, including a harrowing recreation of J.F.K.’s PT 109 heroism, when his boat was sunk in battle and he saved his crew in World War II, and Johnson’s earlier Texas shenanigans, which undermine his integrity.

Robert Kennedy’s loathing for Johnson is traced to some insulting comment made about the Kennedy patriarch, Joseph P. Kennedy, whom President Franklin D. Roosevelt removed as ambassador to the United Kingdom right before the 1940 election. Johnson despised the Kennedy sons because, by his measure, they were not “manly” enough, and he said of Bobby, “I’ll slit his throat if it’s the last thing I do.” Meanwhile, as the 1960 election looms, Johnson now lusts after the presidency and vastly underestimates his rival—as he saw him, a spoiled, sickly lightweight John Kennedy.

With typical cool, J.F.K. calculates that he cannot win the presidency without Texas and inroads into the South; and he offers Johnson the vice presidency. Terrified by the prospect, during the convention Robert Kennedy runs up and down the stairs between his brother’s room and Johnson’s trying to force Johnson out. But Johnson has calculated that the chances of any president dying in office by either illness or assassination were pretty good. So he clings to the vice presidency and endures two years of another kind of humiliation—no power, a too-small office, no clout in the senate, no invitations to the most exclusive parties—aware that the glamorous Kennedy entourage is laughing at him behind his back. He even lowers himself to pleadingly ask Robert Kennedy, “Why don’t you like me?” only to be brushed aside.

Until Dallas. Caro’s prose resurrects the sad reverberating sounds of drum rolls, the clatter of hoofs and rhythmic tread of marching soldiers as the hush deepens block by block.

Caro is not a political cartoonist but a great biographer, a sensitive student of human nature. So the rude, bullying, spiteful Robert Kennedy displays a moral streak during the Cuban Missile Crisis meetings. While most men around the Cabinet Room table want to bomb Cuba, Kennedy, wary of civilian casualties, says, “a sneak attack is not in our traditions.” And he could melt with compassion for sick children and old people in hospital wards.

Lyndon Johnson, a volcanic, abusive vice president facing both a congressional investigation and a Life magazine exposé about Texas political business deals, is transformed by his new role. To win Congressional support for civil rights, tax reform and “the unconditional war on povery” he skillfully creates a two-fisted, mounted frontiersman image by inviting the press to long visits, punctuated by a Van Cliburn concert, at his ranch in Texas. He calls up the image of Jacqueline Kennedy nestling the bloody skull of his predecessor in her lap. As Eric Sevareid said, “He had to stamp his own leadership on his predecessor’s administration, and he did this in a matter of days.... He had to impress his own personality on the country at large, on a people just getting used to Mr. Kennedy’s far different nature, and this Mr. Johnson began to do the moment propriety permitted.”

Meanwhile Robert Kennedy, in deep depression, has been secretly visiting his brother’s grave at night. To the president he is still a “snot-nosed little runt.” Johnson, in a remark he knew would get to Kennedy, later suggested to Pierre Salinger that the assassination might be “divine retribution” for John Kennedy’s “participation” in assassination plots against other heads of state in Cuba and Vietnam. In the next—and final—volume, as Vietnam rises both Kennedy and Johnson will meet their fates. We are blessed to have Robert Caro to tell their stories.

Raymond A. Schroth, S.J., is literary editor of America.