Check out the Youtube clip of Truman resigning as a Democratic delegate at the convention and Kennedy's response.
http://www.youtube.com/watch?v=Xn1d2KsolZg&feature=relatedPrevious Presidents of the same party aren't always happy to see the next generation take over.
Yes, it happens but it doesn't stop it.
SLATER: Let me look.
Oh, I was at his press conference on July 2, 1960, when he announced that he was resigning as a delegate to the national convention because it was controlled, and he thought the Democrats should have an open convention. He said that he had nothing personal against Senator Kennedy. He admired him. He thought he was young, and he thought he ought to be patient. I made some notes
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on this thing. And he said that he's a victim of circumstances. He blamed the kind of campaign, practically delegate buying, on the people around Kennedy. He also at that time at that press conference said he thought that serious consideration should be given to Lyndon B. Johnson.
One story I remember was when he was talking about drinking Scotch whiskey, and he said, "You know everytime you take a drink of Scotch, you're putting a quarter in the pocket of old Joe Kennedy." He didn't think much of the Kennedys on the whole. He said some rather curt things about Joe and then Bobby.
JOHNSON: But then after Jack Kennedy had won the Presidency
SLATER: He supported him all-out, yes.
JOHNSON: And visited him at the White House.
SLATER: At the White House, yes.
JOHNSON: Do you think he really did change his mind
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about John F. Kennedy after he was elected?
SLATER: No.
JOHNSON: Did he gain a little more admiration for him because this policies? Did he feel his policies worked?
SLATER: Never heard him say so. I always thought he kind of felt the Kennedys were exercising too much control over the Democratic party.http://www.trumanlibrary.org/oralhist/slaterh.htm Ask Not What J.F.K. Can Do for Obama
By FRANK RICH
Published: February 3, 2008
BEFORE John F. Kennedy was a president, a legend, a myth and a poltergeist stalking America’s 2008 campaign, he was an upstart contender seen as a risky bet for the Democratic nomination in 1960.
Kennedy was judged “an ambitious but superficial playboy” by his liberal peers, according to his biographer Robert Dallek. “He never said a word of importance in the Senate, and he never did a thing,” in the authoritative estimation of the Senate’s master, Lyndon Johnson. Adlai Stevenson didn’t much like Kennedy, and neither did Harry Truman, who instead supported Senator Stuart Symington of Missouri.J. F. K. had few policy prescriptions beyond Democratic boilerplate (a higher minimum wage, “comprehensive housing legislation”). As his speechwriter Richard Goodwin recalled in his riveting 1988 memoir “Remembering America,” Kennedy’s main task was to prove his political viability. He had to persuade his party that he was not a wealthy dilettante and not “too young, too inexperienced and, above all, too Catholic” to be president.
How did the fairy-tale prince from Camelot vanquish a field of heavyweights led by the longtime liberal warrior Hubert Humphrey? It wasn’t ideas. It certainly wasn’t experience. It wasn’t even the charisma that Kennedy would show off in that fall’s televised duels with Richard Nixon.
Looking back almost 30 years later, Mr. Goodwin summed it up this way: “He had to touch the secret fears and ambivalent longings of the American heart, divine and speak to the desires of a swiftly changing nation — his message grounded on his own intuition of some vague and spreading desire for national renewal.”
In other words, Kennedy needed two things. He needed poetry, and he needed a country with some desire, however vague, for change.http://www.nytimes.com/2008/02/03/opinion/03rich.html