NEW YORK - Robert Caro receives the most interesting mail.
"I get letters, constantly, saying, `I see your book's coming. I hope you're going to prove in this book that LBJ did it,'" the award-winning and ongoing biographer of Lyndon Johnson says during a recent interview at his midtown Manhattan office. "Did it," as in killed President Kennedy.
"When I talk at colleges, you can hardly have a lecture or a speech without one of the first questions being, "Are you going to prove that Johnson did it? Or, are you going to show that Johnson was involved in it?' And when you say Johnson had nothing to with it. You can feel the audience doesn't accept it. You lose your audience."
Believers in Oliver Stone's "JFK" and other conspiracy theorists who hoped that Caro, the most hard-working of historians, would finally nail Johnson will have to look elsewhere. In "The Passage of Power," the fourth of five planned volumes on Johnson, Caro devotes more than 100 pages to the events immediately before, during and after Nov. 22, 1963. Nothing in his many years of research made him suspect Johnson.
"I never came across a single hint, in anything I did - in interviews or all the documents - that would lead you to make such a conclusion," he says.
The Johnson books are an obsession, regardless of who you blame for the death of JFK. Caro has been writing about the late president for nearly 40 years and fans, as anxious in their own way as followers of "Harry Potter," have waited a decade for the latest volume. "Passage of Power" begins in 1958, when Johnson is considering a presidential run; continues through his unhappy time as vice president; and ends in early 1964, weeks after he succeeds Kennedy.
Published this week, the new book is around 700 pages and the series totals more than 3,000; Caro has enough unused material in his filing cabinets to fill many more. Length has not deterred readers or critics. The first three volumes have sold more than 1 million copies. Caro has won two National Book Critics Circle awards, a National Book Award and a Pulitzer Prize, for "Master of the Senate." More honors seem likely for "Passage of Power," which The New York Times' Michiko Kakutani has praised for its "consummate artistry and ardor."
But his influence reaches beyond sales and prizes. The author, who has never held or sought political office, has become a kind of wise man in Washington. According to Ron Suskind's best-selling "Confidence Men," Democratic senators read Caro's books as they attempted to pass health care legislation in 2009 and Rep. Barney Frank consulted "Master of the Senate," which covered Johnson's dominating run as Senate majority leader, as he urged fellow Democrats to support new financial regulation. President Obama has met at the White House with Caro and has said that "The Power Broker," Caro's Pulitzer winner about municipal builder Robert Moses, influenced his own political thinking.
Caro said he hears often from members of Congress. He remembers being asked to visit by Sen. Edward Kennedy's staff several years ago, when Republicans, then in the majority, were threatening to change long-established rules on debate and streamline the voting process. Some called it "the nuclear option," and it was never enacted.
"I think everyone was reading `Master of the Senate,'" says former Kennedy aide Jim Flug, who helped arrange Caro's visit and adds that the historian may have persuaded a couple of legislators to change their minds. "Whenever Bob comes to Washington - I remember a breakfast at the Library of Congress - all the events are always full up. You have people in Washington just listening to every word he says."
Room for the new book already is being made in current political debate. Caro mentions a review in Newsweek by David Frum, a contributing editor for the magazine and former speechwriter for President George W. Bush. Frum greatly admired "Passage of Power" and called it a primer for how a president might lead. He then labeled it an "unspoken critique of President Obama."
"Yes, certainly, Obama shares Lyndon Johnson's gift for driving opponents crazy, if it is a gift," Frum writes. "But the use of power Caro so vividly describes is not something that comes naturally to our current president."
Ridiculous, Caro responds. Any critique is not only unspoken, but "unwritten," "unthought."
"I have a high opinion of Obama," says Caro, praising the president for the health care bill and other legislation.
For Caro, lean and determined at age 76, a sign of achievement is when someone complains about his work. His success rate is high. Johnson aides and family members were angered by his early books on LBJ, especially the second volume, "Means of Ascent," which presented Johnson as vicious and unprincipled as he won a highly questionable Senate race in 1948. But "Master of the Senate" was a redemptive book for both subject and biographer and Caro was welcomed, for the most part, by the Johnson camp. One of his toughest critics, former LBJ aide Jack Valenti, agreed to talk to him for future volumes. The Lyndon Baines Johnson Library and Museum, in Austin, Texas, no longer restricted his access and even began selling his books.
"Passage of Power" offer new opportunities for discussion. Caro suggests in the book that Kennedy might have dropped Johnson in the 1964 election, even though Kennedy himself had said publicly he had no such plan. All agree that the vice president was an outsider in the administration - his opinions ignored, his outsized personality mocked - but the consensus among Kennedy aides and family members has been that the president never seriously considered finding a new running mate.
Caro wonders. He notes that everyone was equally sure Kennedy would not choose Johnson in 1960. Kennedy had picked him in part because Johnson could help ensure support in Texas and other Southern states, but by the fatal visit to Dallas in November 1963, Johnson's influence had fallen enough that Kennedy made some key decisions about the trip in a meeting to which Johnson was not invited. At the same time, an investigation into the finances of Johnson aide Bobby Baker was leading to questions about Johnson himself. Life magazine was planning a long investigation. Congressional hearings had started the morning of Nov. 22.
Given Johnson's lowered standing in Texas and the testimony in Washington, "the president's assurances that he would be on the ticket might start to have a hollow ring indeed," Caro writes.
Caro also questions a narrative dear to Kennedy admirers.
At the time of JFK's assassination, a coalition of Republicans and Southern Democrats were blocking his legislative agenda, including a tax cut and a civil rights bill. Johnson got them passed, along with Medicare, education and other initiatives that Kennedy couldn't get through.
Former Kennedy aides Ted Sorensen and Arthur M. Schlesinger Jr. are among those who have said that those bills also would have gotten through had JFK lived. They reasoned that Kennedy, who won narrowly in 1960, would have been re-elected by a substantial margin and enjoyed larger majorities in Congress.
But Caro points out that the Senate committees were dominated by experienced and conservative Southerners with their own agenda. An especially hard case was Sen. Harry Byrd of Virginia, the deficit hawk and chair of the Senate Finance Committee. He had refused to act on the tax cut bill when Kennedy was in office, but, thanks to LBJ's charm and flattery, eventually cleared it.
"There had been times before (in the 1930s) when (Franklin) Roosevelt had huge majorities in Congress, but after the Southern Democrats decide no more New Deal legislation is going through, no more New Deal legislation goes through," Caro says, adding that obstruction lasted into the 1950s, until Johnson became majority leader.
"Only one guy got bills through - it was Lyndon Johnson."
Caro was friendly with Sorensen, Kennedy's devoted speech writer who died in 2010. They were neighbors on Manhattan's Upper West Side and would meet often, the two sitting on opposite couches in Sorensen's apartment, overlooking Central Park. Sometimes, they would discuss whether Kennedy could have gotten his legislation passed.
"I remember going over this again and again with Sorensen," Caro says. "He wouldn't agree with me."
The historian says the book tells two stories: "The deep hatred" between Johnson and the Kennedys, especially Robert Kennedy, and what happens when JFK is dead and roles are overturned. Johnson, the unwanted vice president, is in charge.
"That's why I call the book `Passage of Power.' The title is what it is. You examine something in its moment of greatest crisis and you see what it has to do," Caro says. "To watch Lyndon Johnson grab up the reins of power and get Kennedy's legislation moving, how he keeps the people in the Kennedy administration from leaving and reassures the American people, is to see political genius in action."
Caro has called Johnson a story of darkness and light, and clouds will gather in Volume V, which Caro expects to complete within the next few years. Among what happened during Johnson's last decade: His landslide victory in 1964; his fateful decision in 1965 to commit ground troops to Vietnam; the rapid passage of historic bills, including on civil rights, education and immigration; Robert Kennedy's brief run against Johnson for president in 1968; the assassinations of Kennedy and Martin Luther King Jr.; Johnson's announcement that he would not seek another term; his final years back in Texas and his death, in 1973.
The book, Caro says, will be long.