Harry Truman was probably more conservative than Ike.
JFK was more conservative than Ike. By today’s definitions, JFK is a neocon.
Spot on, and so was the article. Historically, Republicans were not the conservative party. In the late fifties, early sixties, they had two wings, the Rockefeller wing and the Goldwater wing. The Goldwater wing could almost be considered the Goldwater feather. It was never a majority of the Republican party, and Reagan is still the only member of the Goldwater wing to actually be elected, although both Bushes ran more as Reaganites than Rockefellers.
John Kennedy, before his assassination, was hoping to run against Goldwater, whom he knew he would beat easily. He felt fortunate to have run against Nixon in 1960, because Nixon was a west coast Republican. He did not believe he could beat a Republican from the Rockefeller wing of the party, either in 1960 or 1964.
The conservative Republican was an offshoot of mainstream Republicanism, with Goldwater as the prophet and Reagan as the Messiah.