The Ehrlichman quote was first published by Dan Baum in his 1997 book, Smoke and Mirrors. This book came out before Ehrlichman died, and it included other interviews with Nixon staffers that supported the Ehrlichman quote. The book was reviewed by the New York Times.
I believe that this quote was not published in that book, and instead he "remembered" the quote years after the book was published to put in a Harper's article. He chose not to publish it in the book because he was focused on first hand accounts of the time period, not people's statements in retrospect.
Do you know the page number this quote appears on?
