Trump becoming 'brazenly megalomaniacal' -- and 'it will only get worse': 'Art of the Deal' ghostwriter Tony Schwartz
Tony Schwartz co-wrote the 1987 book 'The Art of the Deal' with Donald Trump

President Donald Trump's ghostwriter for "The Art of the Deal" interrupted his vacation to warn that the former reality TV star's mental state appears to be dissolving before the public eye.

Tony Schwartz, who spent hundreds of hours with the future president working on the 1987 book that defined his public persona as a celebrity businessman, has warned since the 2016 campaign that Trump is dangerously unfit for office.

On Thursday morning, he issued another urgent warning based on the president's recent behavior, which includes comparing himself to the "second coming" and declaring himself the "chosen one."

"On vacation, but feel compelled to share this," Schwartz tweeted. "Trump seems more unmoored from reality and more brazenly megalomaniacal than I have ever observed before. And it will definitely get worse."