Let's roll the tape.
And guess what? "By the standards of the day," he was clearly seen by liberals as a liberal.
Throughout his career in the House and Senate, the ADA rated John F. Kennedy as liberal year after year.
The @newrepublic, for instance, looked over Kennedy's congressional career from 1947-1958 and gave him a 91% liberal rating.
You're welcome to judge him by your own standards, but "by the standards of his day," JFK was absolutely *not* seen as a "conservative Democrat." He was rightly recognized as a liberal.