A co-author of President Trump's 1987 best-selling memoir, "Art of the Deal," is predicting the president will resign from office before the end of the year. 

“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 said Thursday, referring to special counsel Robert Mueller, who was appointed by the FBI to lead the federal investigation into whether Trump's campaign colluded with Russia to influence the outcome of the 2016 presidential election.

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"Trump must be isolated. Resistance every day. The end is near but must keep pressure high," he added.

Schwartz made a similar prediction in May when he said that Trump would resign because he was in "pure terror" over the ongoing investigation by Mueller.

“There is no right and wrong for Trump. There’s winning and losing. And that’s very different from right and wrong. Right now he’s in pure terror that he is going to lose," Schwartz said in May.

"And, by the way, he is going to lose.”