I also am not sure that Kennedy would have done more harm than Nixon did with his other policies.
I never said we "Won" the war. What I said is that while Nixon was in office, after the Paris Peace Accords of 1973, South Vietnam was a functioning country albeit with a lot of financial and strategic support from us and more than holding their own against an aggressive enemy who had massive support from the Soviet Union.
When the new decidedly 'leftist' Congress after Watergate cut that aid and support, South Vietnam was alone and isolated with no hope of survival.
It was a crime in my opinion and yet there are still members of congress who are proud they allowed a holocaust in Vietnam and across S.E. Asia.
I still hate those bastards. I will till my dying breath.
As to what I would have done...
JFK... who knows, but my best guess is he would have screwed up as bad as Johnson because neither had a clue outside of domestic politics and both relied on the same incompetent foreign policy team.
LBJ... after the NVA violated the TET cease fire, I would have pulled all of our diplomats away from the phony Paris peace talks, sent another 100,000 ground troops in to wipe out the remaining NVA troops in S. Vietnam and Cambodia, bombed Hanoi into the stone ages and mined Haiphong harbor just as Nixon finally did 4 years later.
Nixon in 1969... see above.
We saw that incrementalism and Robert Strange McNamara's 'gradual' escalation are folly when it comes to war. You either fight to win, or you don't fight at all. (See Goldwater in 1964.)