Supposedly, Ronald Reagan in a private letter, called him a Marxist in 1960.
I’d be disappointed if Reagan really thought that. Kennedy had plenty of faults but sympathy for Communism was never one of them. Our confrontation with the Soviets over Berlin in 1961, with the Soviets over the Cuban missile crisis in 1962, his ramping up our role in Vietnam, his wiretaps of MLK over Hunter Pitts ODell and Jack Levison all argue against it.