The second most-asked question about the brutally truncated Kennedy administration--the most-asked question being that truly idiotic one, Who killed Kennedy?--is whether the 35th president would have bogged us down in South Vietnam, as his successor did.
Lyndon Johnson's unflinching answer of "yes" was always self-interested, as, to some extent, are everyone's answers. Ordinarily they tell us more about the respondent--if he or she admires John Kennedy, then the answer is "no," with the corresponding opposite among non-admirers. Thus you can take my opinion for the worth I just assigned it.
My opinion is no, JFK would not have bogged us down in the manner of LBJ. Kennedy's learning curve in the White House spiked after the disastrous Bay of Pigs, and his education was immersed principally in suspicion--suspicion of U.S. intelligence, suspicion of military minds, suspicion of the best and the brightest and, above all, the hawkish.
Yet his public signals suggested confidence, as politically they had to. Kennedy was facing the aggressively anticommunist Barry Goldwater in the '64 campaign, so his support of that era's popular foreign policy theories, dominoes and all, was, for public consumption, indispensable. After Goldwater, however, Kennedy could more overtly be his own man, which as president he had indeed become. In reviewing his record of a growing intellectual independence from the assorted Wise Men of the early 1960s, I have come to believe that Kennedy would have pulled back from Southeast Asia, having recognized it as the bottomless sinkhole it was.
Perhaps the pithiest observation of Kennedy as president I've ever read comes not from a historian, but from the novelist Saul Bellow, who in Herzog meditated that Eisenhower's "tragic successor would have been interested" in difficult questions about our deepest "national purpose," but not Ike, "nor Lyndon. Their governments could not function without intellectuals--physicists, statisticians--but these are whirling lost in the arms of industrial chiefs and billionaire brass. Kennedy was not about to change this situation, either. Only he seemed to have acknowledged, privately, that it existed."
That, I'd say, is an incisively fair assessment of Kennedy's push-pull growth in office. And because of his overall growth, I'd venture that ultimately he would have drawn a line when came to the dire prospect of risking so many American lives in Vietnam. In sum I believe others' intellectual abstractions would, for Kennedy, have turned very real, and he, in turn, would have backed off.