No, he was not.
One contemporary author, Ira Stoll, has made this claim in a new book, but no conservative thinker alive during JFK presidency ever expressed the thought,
In fact, the leading voices of the American right in the early 1960 including Clare Booth Luce, William F. Buckley, William Rusher, and Barry Goldwater reviled Kennedy for his liberal policies, especially on civil right and Cuba.
In a piece for Salon.com Paul Rosenberg punts Stoll and other right-wing polemicists who attempt to co-opt Kennedy’s popularity for contemporary conservatism.
Stoll’s argument is so implausible that Rosenberg ultimately concludes it is not factual.
“It’s not just that Stoll is wrong on the facts. He has utter contempt for them. He is not even trying to make a factual argument. He’s only trying to create the appearance of one … he’s going through the motions of pretending to show Kennedy was a conservative, so that other conservatives can pretend to be convinced. It’s a form of play-acting ritual, meant to claim Kennedy as a member of the conservative tribe. This is not a rational exercise, but an ethno-religious one.?
JFK is most accurately characterized as a center-left president
See also in JFK Facts:
JFK’s foreign policy: Douglas Horne v. Robert Dallek (Oct. 29, 2013)
What the New York Times doesn’t get about JFK and Vietnam (Oct. 29, 2103)