Story highlights Tony Schwartz spent 18 months with Trump in the 1980s

'The Art of the Deal' was published in 1987

Washington (CNN) The ghostwriter of "The Art of the Deal" thinks President Donald Trump will eventually call it quits.

Tony Schwartz, the man behind Trump's 1987 memoir, took to Twitter on Wednesday to vocalize his forecast for Trump's political future.

"The circle is closing at blinding speed," Schwartz tweeted. "Trump is going to resign and declare victory before Mueller and congress leave him no choice."

The circle is closing at blinding speed. Trump is going to resign and declare victory before Mueller and congress leave him no choice. — Tony Schwartz (@tonyschwartz) August 16, 2017

In a follow-up tweet, he added: "Trump's presidency is effectively over. Would be amazed if he survives till end of the year. More likely resigns by fall, if not sooner."

Trump's presidency is effectively over. Would be amazed if he survives till end of the year. More likely resigns by fall, if not sooner. — Tony Schwartz (@tonyschwartz) August 16, 2017

While working on the memoir in the 1980s, Schwartz spent 18 months with Trump. Over the past few years, he has been an outspoken critic of the former businessman, now President.

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