Don’t forget Richard Nixon. Not only did he lose to JFK in 1960, he lost the CA Governorship in 1962. He became a joke to news junkies of the day. FDR and Nixon were able to comeback due to screw ups by incumbent Presidents.
At this stage, I don’t see the GOP ever winning the White House without a Dem President screwing up.
Nixon wasn’t a losing VP candidate, he was a losing Presidential candidate.
But yes, both made comebacks because of incumbent screw-ups.