The "consensus" today is that the 1960 election was stolen from Nixon (at the time Ike's VP) and given to JFK though ballot box stuffing in at least two select key swing states: Illinois though the efforts of the Daley Democrat political machine and in Texas through LBJ's network of southern Democrats. Remember, Texas went for Ike twice; it was a swing state back then.
This consensus comes from mounds of work by investigative journalists, professional historians, political scientists and others. Nobody doubts it today, though not that many people talk about it, because, seriously, how often does the 1960 election come up. Only the ignorant, and there are many, don't know about how Nixon was robbed in 1960.
Nixon did not contest the election, because he thought the country would be ungovernable even if he won. It was still ungovernable when he won later. The left set out to destroy him from day 1 of his term, so he wasn't wrong.
The thing is, this "consensus" took about 40 years to form. There was a pall cast over the issue until it was safe, given the distance of time, to look dispassionately at the data. But form it did, because there was to much evidence for voter fraud there not to be a consensus on the issue.
I'm in my 40s. I think I may see in my lifetime that the historians, political scientists, journalists, and general academics at least two generations from now will, when it requires no bravery, admit that the 2020 election was stolen from Trump.