Donald Trump s onetime ghostwriter, Tony Schwartz, told CNN on Monday night that he is advising Hillary Clinton s campaign for free, in an effort to make up for having contributed to Trumps rise to fame in the 1980s.

This is my penance for having created a man who has become a monster, and Ive spent 30 years feeling bad about it, Schwartz said. Now I feel like Ive got to show that theres nobody behind the curtain.

Schwartz was the ghostwriter on Trumps first book, The Art of the Deal, which went on to become a best-seller. He spent over a year working closely with Trump on the book, and got to know the businessman well.

He has been one of Trumps most outspoken critics ever since the real estate mogul announced his presidential campaign.

Schwartz paused when CNN asked him to name one thing about Trump that he found appealing.

There was nothing I found appealing, he said. This is a man who I really believe lacks a conscience at the deepest level, so there really was nothing. He was effective in certain ways, hes a dominant, aggressive personality and he pushes and he pushes and he pushes and he gets a lot of what he wants.

Trumps attorneys threatened to sue Schwartz for defamation after The New Yorker published a profile of him this summer.

Editors note: Donald Trump regularlyincitespolitical violence and is a