Robert Caro writes — and writes and writes — about LBJ in ‘The Passage of Power’

President Lyndon Baines Johnson lived 64 years. Robert Caro has been examining that life for about 35.

“I don’t like to be rushed,” he told me early in April. We met in the room where Caro wrote the fourth volume of his Johnson biography. It is not the last. “The Passage of Power” brings Caro’s work on Johnson to more than 3,000 pages. Only near the end of his most recent book has Caro arrived at the beginning of Johnson’s presidency, which lasted from 1963 to 1969.

Each time he releases another volume — usually after an interval of eight to 12 years — Caro provokes astonishment that he would devote so much time to one subject. He’s been compared more than once to Ahab, Melville’s one-legged captain obsessed with Moby Dick.

The comparison is a bit morbid. Ahab’s life did not end well. The Columbia Journalism Review asked a decade ago if Caro’s excessive interest in Johnson had “led him astray,” and his 80-year-old editor has told the New York Times that he doesn’t expect to live to edit Caro’s final book.

But Caro’s meticulous process delivers powerful results. A onetime newspaper reporter, he abandoned that deadline-oriented mind-set long ago. In a world of snap judgments and ephemeral facts, he makes exceptional use of the commodity that modern journalists have the least of: time.

Now 76, Caro exhibits a youthful enthusiasm when discussing his work among the bookshelves and filing cabinets of his Manhattan office. Saying that he would be too “lazy” if he worked at home, he has commuted to this room for decades. Almost nothing in the office betrays the arrival of the 21st century. His inbox is an inbox. He does use a computer for research, as he says the LBJ Library complained about his clacking typewriter.

For his LBJ biographies, Caro supplemented exhaustive digging by interviewing those who knew Johnson, who died in 1973. He temporarily moved with his wife, Ina, to Johnson’s home state of Texas, driving into the countryside outside Austin to sit with the president’s relatives and boyhood classmates. He met other aging sources in their offices, continued calling after they entered nursing homes and preserved his notes for years after they died.

The roster of available interviewees is thinning — “The human life span is my biggest obstacle,” Caro said — but he occasionally finds one more. In 2008, when he learned that Cecil Stoughton, who photographed Johnson’s swearing-in after John F. Kennedy’s assassination in 1963, was still alive, Caro picked up a phone. Stoughton’s wife answered.

“Mrs. Stoughton, my name is Robert Caro,” the author recalled saying. “And she says, ‘Cecil has been waiting on you to call.’ ”

Caro weaves the photographer’s memories into a pivotal section of “The Passage of Power.” In the new volume, Johnson, desperate to lead, was trapped in a powerless vice presidency, irrelevant and despondent. “In the crack of a gunshot it [was] reversed,” Caro said. The new president had to reassure a traumatized nation and begin driving Kennedy’s legislative agenda through Congress.