The left had a grudge against Nixon from way back to the Alger Hiss case. Dean Acheson hated him, and was still alive in the early years of the Nixon administration when the campaign against Nixon began. Acheson's chief assistant Paul Nitze survived him and managed to get into the Nixon administration, then created a scene when he resigned a few years later. John Ehrlichman told Nixon he was "quite sure" Nitze was one of the co-conspirators in the Pentagon Papers leak. IMO there are indicators like this that the antiwar campaign against Nixon had some very high-level help from people in the Democratic Party trying to undermine Nixon using the Vietnam controversy as a weapon. Ted Kennedy played a big role in the Watergate prosecution. Kerry's associate Robert Drinan also played a pivotal role, introducing the impeachment proceedings. I hope to do a more thorough investigation of this angle later.