Remember that Nixon's original likely D opponent in the 1972 general election would have been Edmund Muskie, who was actually polling better than Nixon in late 1971-early 1972. Nixon's dirty tricksters like Donald Segretti spent large amounts of time to destroy Muskie, who eventually pulled out. That left George McGovern, who was the one the Nixon folks wanted to run against because McGovern was more left than the other candidates. And they trounced him.
(Incidentally, trump tried to do the same thing when he was trying to smear Joe Biden with the Ukraine initiative. It was laughable to the extreme that the idiot went around saying he wasn't worried about defeating Joe Biden, but someone like Bernie Sanders was who he feared. Don't get me wrong: I have extreme respect for Senator Sanders. But when trump himself said something like this, it made me realize that he feared Biden. Why else would he have risked impeachment to get dirt on Biden, but on no one else? The analogy to Nixon and Muskie/McGovern shouldn't be lost. trump was dumb enough to hilight this front and center.)
And remember the Watergate burglary in June 1972 and the massive efforts to cover-up that it was a Nixon operation, including by campaign leadership and staff. It would have been disastrous for Nixon's re-election campaign if the truth that the burglary was, to a large degree, agreed to by John Mitchell, when he was Attorney General and then after he became head of Nixon's re-election campaign. The cover-up was largely to win the re-election.
The corruption and criminality of Nixon was incredible, and trump is a direct outcome of that (and, by the way, both Nixon and trump had Roger Stone!....as did Reagan, and Bush I.)