It is so difficult to say, events of great moment turned on an hour-long meeting during his Presidency. He lost a great deal of ground over the Bay of Pigs fiasco, but still had an adoring press eating out of his hand; unemployment was high and his large-scale Reserve call-up for the Berlin crisis pissed off a lot of people adversely affected by it; civil rights issues were a lightning rod and while he was on the right side of it morally, he was losing the Southern Dems who likely would have defected en masse at the next election; and though we didn't find out about it until the USSR collapsed, he came within a day of plunging us into nuclear war with the Reds - missiles were armed and ready in Cuba and the Red commander on the ground had release authority and every intent to fire them on Eastern Seaboard targets if we dropped troops in, which was exactly what the military was advocating, through more good luck than brainpower JFK decided not to do that. His machinations in Viet Nam were headed into a bottomless pit, but had he lived would it have gotten there faster, or slower? There is a very real chance he would not have been re-elected, despite the leg-humping of the all-powerful three major networks, Time-Life, and the WP/NYT.