She said her husband and his brother then-Attorney General Robert F. Kennedy, a longtime LBJ antagonist, even discussed ways to prevent Johnson from winning the Democratic nomination in a future contest.
The book, "Jacqueline Kennedy: Historic Conversations on Life with John F. Kennedy," includes a series of interviews the former first lady gave to historian and former Kennedy aide Arthur M. Schlesinger Jr. shortly after her husband was assassinated on Nov. 22, 1963. Over seven sessions, she recalled conversations on topics ranging from her husband's reading habits to the botched Bay of Pigs invasion in Cuba.
The book will be published by New York-based Hyperion Books on Sept. 14. Its release comes on the 50th anniversary of Kennedy's first year in office. The Associated Press bought a copy Thursday.
JFK chose Johnson, a Texas senator and former political rival, as his running mate in 1960. But Jacqueline Kennedy told Schlesinger in the 1964 interviews that he often fretted about the prospect of a Johnson presidency.
"Jack said it to me sometimes. He said, `Oh, God, can you ever imagine what would happen to the country if Lyndon were president?"' she recalled. "And Bobby told me that he'd had some discussions with him ... do something to name someone else in 1968."
Johnson was sworn in as president after JFK's assassination and was elected to a full term in 1964. He declined to seek re-election in 1968.
Jacqueline Kennedy also indicated that her husband was highly skeptical about victory in Vietnam, a central battleground of the Cold War and the conflict that brought down Johnson's presidency. She said that JFK, a Democrat, had named Henry Cabot Lodge, a Republican he had defeated for a Massachusetts Senate seat in 1952, as U.S. ambassador to Vietnam because JFK was so doubtful of military success there.
"I think he probably did it ... rather thinking it might be such a brilliant thing to do because Vietnam was rather hopeless anyway, and put a Republican there," Jacqueline Kennedy said.
JFK increased the U.S. presence in Vietnam throughout his brief administration, adding military advisers to help train the South Vietnamese military. Johnson, as president, would later commit ground troops to the conflict despite initial promises not to. Historians still debate whether Kennedy would have done the same.
Jacqueline Kennedy spoke skeptically of civil rights leader Martin Luther King Jr. She called him "tricky" and a "phony" after hearing about FBI tapes of King and a woman in his hotel room, while noting that President Kennedy had urged her not to be judgmental. (Kennedy's own adulterous affairs were not yet widely known.) She said King had mocked her husband's funeral and Cardinal Richard Cushing, who celebrated Mass at the funeral.
"He made fun of Cardinal Cushing and said that he was drunk at it," she said. "And things about they almost dropped the coffin. I just can't see a picture of Martin Luther King without thinking, you know, that man's terrible."
The book comes with eight audio CDs of the interviews. Jacqueline Kennedy's voice is firm and girlish, even and clear, but the interviews are occasionally interrupted by sounds of her children, Caroline, who was 5 at the time, and John Jr., who was 3. At one point, Schlesinger asks young John if he knows what happened to his father. "He's gone to heaven," the boy replies. Schlesinger asks what he remembers. "I don't remember ANY-thing," John says playfully.
The book barely mentions the president's assassination. In a foreward, Caroline Kennedy notes her mother had discussed his murder at length with historian William Manchester, but later sued to keep much of the material from being published until 2067. Manchester's book on Kennedy, "The Death of a President," came out in 1967.
Jacqueline also gave a memorable interview with journalist Theodore H. White, when she referred to her husband's time in the White House as "Camelot," but Caroline Kennedy said the interviews in the new book were "by far the most important" her mother ever gave. Jacqueline Kennedy died in 1994.
"My mother willingly recalled the span of her married life and shared her insights into my father's private and public political personality," Caroline Kennedy wrote.
The former first lady and Schlesinger, who died in 2007, at times sound like a couple of old friends sharing gossip, ridiculing Richard Nixon's wife, Pat, or labeling LBJ's wife, Lady Bird, as so obedient she was like a "trained hunting dog." (Jacqueline Kennedy would later soften that opinion.)
At other times, the scholarly Schlesinger fills her in on details about her husband before she knew him or corrects a name or date. Jacqueline Kennedy, clearly at ease, speaks candidly about her in-laws and about other Kennedy insiders.
She marvels at the suspicious nature of her mother-in-law, Rose Kennedy, always wanting to know whether someone was Catholic.
"There seems to be about all these Irish - they always seem to have a sort of persecution thing about them, don't they?" she asks.
She also accuses sister-in-law Eunice Kennedy Shriver of undue personal ambition and says the president was anxious to dump FBI chief J. Edgar Hoover. She confides she didn't trust the White House aide and speechwriter Theodore Sorensen, believing that Sorensen encouraged the perception that he had ghostwritten her husband's Pulitzer Prize-winning "Profiles in Courage."
"You know, Jack forgave so quickly, but I never forgave Ted Sorensen," she said of Sorensen, who was widely regarded as devoted to JFK. She said the president, out of personal fondness, even gave Sorensen the book's royalties. Sorensen died in 2010.
She offers intimate details of her husband awaiting election results in 1960, when he defeated Nixon for the presidency, or working on his inaugural speech. She says little about the events in Dallas on Nov. 22, 1963, but she does recall a conversation in their room the night before. Jacqueline Kennedy despised the governor of Texas, John Connally, who was in the same car as the Kennedys when the president was shot.
"I just can't stand Governor Connally. I can't stand his soft mouth," she said about the Texas Democrat.
"Jack was so sweet. He sort of rubbed my back ... and said, `You mustn't say that, you mustn't say that,"' she recalled. "If you start to say or think that you hate someone, then the next day you'll act as if you hated him."