Kennedy (D), of course. A Nixon victory in 1960 would only have accelerated the "southern strategy"- why do you think he screamed at Lodge when he promised to appoint a "Negro" to the Cabinet?
I don't think cutting off right-wing "Democrats" in the South was a bad thing.
Kennedy, on the other hand, very much campaigned in a right-wing manner. His main difference from Nixon was that he would escalate the Cold War from Eisenhower's levels. In addition, it would have left Lyndon Johnson a heartbeat away from the Presidency, as Libertas so eloquently put it.