[citation needed], and not the citation from an interview twenty years ago with a guy long dead, who quoted Erlichman in an unfinished book.

It was really John Ehrlichman who revealed the truth. Listening to the Nixon tapes, he (Nixon) spent the entirety of his days scheming against political enemies and people he simply didn't like.

https://www.cnn.com/2016/03/23/politics/john-ehrlichman-rich...

You really shouldn't need a citation for something so easily verifiable.