In retrospect, he spent his 35 months in the White House stumbling from crisis to fiasco. He came into office and okayed the Bay of Pigs invasion. Then he went to a Vienna summit conference and got his clock cleaned by Khrushchev. That led to, among other things, the Cuban missile crisis and a whiff of nuclear apocalypse.
Looming over it all is the American descent into Vietnam.And there's more.
I think Kennedy's domestic record was even worse. Most of what we remember about him is a fiction created after his death. The real man was undoubtedly a disaster, but to name him as the worst? I dunno. There's a lot of competition there at the bottom.
Read Ricks' article here.