Until Nixon was undone by Watergate, he had planned a major housecleaning of the federal government, including the FBI and CIA. Moreover, Nixon was telling staffers that the Warren Report was a fraud and that Kennedy was killed by a plot set in motion by LBJ and using in part CIA connected Cuban exiles furious over Kennedy's betrayal at the Bay of Pigs.
Watergate Committee staffers privately warned their bosses that Nixon's actions had precedents in prior administrations. At trial in the Senate, Nixon could have mounted a persuasive defense on the merits that might have saved his Presidency. In any event, such a defense by Nixon would have spilled many secrets that official Washington did not want exposed.
I didn't know until recently that Kennedy also betrayed the anti-Communists in another revolution--Vietnam--by ordering the US agents to assassinate Ngo Diem, the very popular, duly elected President of South Vietnam, who had been President of all of Vietnam before the Communist invasion.
After the invasion of the Communists from the North, Diem was the country's only proven leader, and was the brains behind the only military tactic that was working against the Communists: training and arming the individual towns (where the highly motivated locals knew the terrain) to defeat the invaders.
Makes you wonder which side Kennedy and his government were on.
There were no promises of a pardon. Not true