Tony Schwartz, Co-Author of Donald Trump's 'The Art of the Deal,' Says Trump Presidency Would Be 'Terrifying' Tony Schwartz admitted that he regrets writing the 1987 book.

 -- Tony Schwartz, Donald Trump’s co-author on “The Art of the Deal,” admitted that he regrets writing the 1987 book and that he finds the thought of a Trump presidency “terrifying.”

So why did Schwartz keep his silence for so long?

“We had a successful experience together. I never in a million years thought he would run for president. Had I thought that 30 years ago, I wouldn’t have written the book,” he told George Stephanopoulos on ABC News’ “Good Morning America” today. “But for 29 years, I didn’t think he would, and it didn’t seem like it was important to speak out. I now feel it’s my civic duty.”

Schwartz first spoke out about Trump in an interview with The New Yorker published today, in which he said he spent 18 months getting to know Trump in 1985. He described what it was like to write the book with the businessman and how he thinks he would do as president of the United States.

“I put lipstick on a pig,” Schwartz told the magazine. “I feel a deep sense of remorse that I contributed to presenting Trump in a way that brought him wider attention and made him more appealing than he is.”

He added, “I genuinely believe that if Trump wins and gets the nuclear codes, there is an excellent possibility it will lead to the end of civilization.”

Schwartz, the president and CEO of the Energy Project, stood by his comments on “GMA” this morning.

“You know, it’s a terrifying thing. I haven’t slept a night through since Donald Trump announced for president because I believe he is so insecure, so easily provoked and not — not particularly — nearly as smart as people might imagine he is,” he said. “I do worry that with the nuclear codes, he would end civilization as we know it.”

He continued, “This is a man who has more sociopathic tendencies than any candidate in my adult life that I’ve observed.”

Schwartz said he wrote “every word” of “The Art of the Deal,” Trump’s part memoir and part business advice book, which held the No. 1 spot on the New York Times’ nonfiction best-seller list for 51 weeks.

“Donald Trump made a few red marks when I handed him the manuscript, but that was it,” he said.

When told about Schwartz’s remarks, Trump told The New Yorker, “He’s probably just doing it for the publicity.”

He added, “Wow. That’s great disloyalty, because I made Tony rich. He owes a lot to me. I helped him when he didn’t have two cents in his pocket. It’s great disloyalty. I guess he thinks it’s good for him — but he’ll find out it’s not good for him.”