We all know what a tiny, insecure man Donald Trump is. The slightest hit to his ego is enough to send lawyers scrambling and the late night Twittersphere burning.

When the ghostwriter for his 1987 book, “The Art of the Deal” recently stepped forward to express concerns about somebody like Trump having access to the nuclear codes, the predictable happened.

Tony Schwartz, the ghostwriter of Mr. Trump’s best-selling autobiography “The Art of the Deal,” said on Wednesday that he had received a cease-and-desist letter from Mr. Trump’s chief legal counsel over his blistering assessments of the candidate and their work together.

Mr. Schwartz said in an interview with MSNBC that the letter demanded that he forfeit all royalties he had earned from the book.

“It’s nuts and completely indicative of who he is,” Mr. Schwartz said. “There’s no basis of anything legal. I suspect that Donald Trump called up his chief legal officer and said, ‘Go after that guy and do whatever you have to do.’ ”

He added, “So this poor head of legal affairs for the Trump Organization had to concoct stuff — most which of is untrue.”

Mr. Schwartz spent 18 months shadowing Trump, learning about the man, and he’s now feeling remorse for possibly giving the impression that Trump was a reasonable or successful leader.

The facts of who Mr. Schwartz remembers are quite different. While Trump has touted the book as a sign of his success, Schwartz insists it’s fiction, meant to pump up the image of a thin-skinned, self-centered man, with a short attention span.

In a copy of the cease-and-desist letter obtained by The New York Times, the lawyer, Jason D. Greenblatt, demanded that Mr. Schwartz deliver “a certified check made payable to Mr. Trump” and make “written assurances that you will not generate or disseminate any misleading or inaccurate information or make any baseless accusations with respect to Mr. Trump.”

In a brief phone interview after the convention speeches ended on Wednesday evening, Mr. Trump painted Mr. Schwartz as a disgruntled former partner.

“He’s been trying to get work from me for 30 years,” Mr. Trump said. “He wrote me letters” asking for work, he added. “I never liked him.”

That always seems to be Trump’s answer. If somebody speaks out against him, it’s because they are either disgruntled, or wanted to work for him and were turned down.

It can’t be everybody, Donnie. There’s a common denominator in there, somewhere.

It’s you.