Growing desperate, Schwartz devised a strategy for trapping Trump into giving more material. He made plans to spend the weekend with Trump at Mar-a-Lago, his mansion in Palm Beach, where there would be fewer distractions. As they chatted in the garden, Ivana icily walked by, clearly annoyed that Schwartz was competing for her husband’s limited free time. Trump again grew impatient. Long before lunch on Saturday, Schwartz recalls, Trump “essentially threw a fit.” He stood up and announced that he couldn’t stand any more questions.

Schwartz went to his room, called his literary agent, Kathy Robbins, and told her that he couldn’t do the book. (Robbins confirms this.) As Schwartz headed back to New York, though, he came up with another plan. He would propose eavesdropping on Trump’s life by following him around on the job and, more important, by listening in on his office phone calls. That way, extracting extended reflections from Trump would not be required. When Schwartz presented the idea to Trump, he loved it. Almost every day from then on, Schwartz sat about eight feet away from him in the Trump Tower office, listening on an extension of Trump’s phone line. Schwartz says that none of the bankers, lawyers, brokers, and reporters who called Trump realized that they were being monitored. The calls usually didn’t last long, and Trump’s assistant facilitated the conversation-hopping. While he was talking with someone, she often came in with a Post-it note informing him of the next caller on hold.

“He was playing people,” Schwartz recalls. On the phone with business associates, Trump would flatter, bully, and occasionally get mad, but always in a calculated way. Before the discussion ended, Trump would “share the news of his latest success,” Schwartz says. Instead of saying goodbye at the end of a call, Trump customarily signed off with “You’re the greatest!” There was not a single call that Trump deemed too private for Schwartz to hear. “He loved the attention,” Schwartz recalls. “If he could have had three hundred thousand people listening in, he would have been even happier.”

This year, Schwartz has heard some argue that there must be a more thoughtful and nuanced version of Donald Trump that he is keeping in reserve for after the campaign. “There isn’t,” Schwartz insists. “There is no private Trump.” This is not a matter of hindsight. While working on “The Art of the Deal,” Schwartz kept a journal in which he expressed his amazement at Trump’s personality, writing that Trump seemed driven entirely by a need for public attention. “All he is is ‘stomp, stomp, stomp’—recognition from outside, bigger, more, a whole series of things that go nowhere in particular,” he observed, on October 21, 1986. But, as he noted in the journal a few days later, “the book will be far more successful if Trump is a sympathetic character—even weirdly sympathetic—than if he is just hateful or, worse yet, a one-dimensional blowhard.”

Eavesdropping solved the interview problem, but it presented a new one. After hearing Trump’s discussions about business on the phone, Schwartz asked him brief follow-up questions. He then tried to amplify the material he got from Trump by calling others involved in the deals. But their accounts often directly conflicted with Trump’s. “Lying is second nature to him,” Schwartz said. “More than anyone else I have ever met, Trump has the ability to convince himself that whatever he is saying at any given moment is true, or sort of true, or at least ought to be true.” Often, Schwartz said, the lies that Trump told him were about money—“how much he had paid for something, or what a building he owned was worth, or how much one of his casinos was earning when it was actually on its way to bankruptcy.” Trump bragged that he paid only eight million dollars for Mar-a-Lago, but omitted that he bought a nearby strip of beach for a record sum. After gossip columns reported, erroneously, that Prince Charles was considering buying several apartments in Trump Tower, Trump implied that he had no idea where the rumor had started. (“It certainly didn’t hurt us,” he says, in “The Art of the Deal.”) Wayne Barrett, a reporter for the Village Voice, later revealed that Trump himself had planted the story with journalists. Schwartz also suspected that Trump engaged in such media tricks, and asked him about a story making the rounds—that Trump often called up news outlets using a pseudonym. Trump didn’t deny it. As Schwartz recalls, he smirked and said, “You like that, do you?”

Schwartz says of Trump, “He lied strategically. He had a complete lack of conscience about it.” Since most people are “constrained by the truth,” Trump’s indifference to it “gave him a strange advantage.”

When challenged about the facts, Schwartz says, Trump would often double down, repeat himself, and grow belligerent. This quality was recently on display after Trump posted on Twitter a derogatory image of Hillary Clinton that contained a six-pointed star lifted from a white-supremacist Web site. Campaign staffers took the image down, but two days later Trump angrily defended it, insisting that there was no anti-Semitic implication. Whenever “the thin veneer of Trump’s vanity is challenged,” Schwartz says, he overreacts—not an ideal quality in a head of state.

When Schwartz began writing “The Art of the Deal,” he realized that he needed to put an acceptable face on Trump’s loose relationship with the truth. So he concocted an artful euphemism. Writing in Trump’s voice, he explained to the reader, “I play to people’s fantasies. . . . People want to believe that something is the biggest and the greatest and the most spectacular. I call it truthful hyperbole. It’s an innocent form of exaggeration—and it’s a very effective form of promotion.” Schwartz now disavows the passage. “Deceit,” he told me, is never “innocent.” He added, “ ‘Truthful hyperbole’ is a contradiction in terms. It’s a way of saying, ‘It’s a lie, but who cares?’ ” Trump, he said, loved the phrase.

In his journal, Schwartz describes the process of trying to make Trump’s voice palatable in the book. It was kind of “a trick,” he writes, to mimic Trump’s blunt, staccato, no-apologies delivery while making him seem almost boyishly appealing. One strategy was to make it appear that Trump was just having fun at the office. “I try not to take any of what’s happened too seriously,” Trump says in the book. “The real excitement is playing the game.”

In his journal, Schwartz wrote, “Trump stands for many of the things I abhor: his willingness to run over people, the gaudy, tacky, gigantic obsessions, the absolute lack of interest in anything beyond power and money.” Looking back at the text now, Schwartz says, “I created a character far more winning than Trump actually is.” The first line of the book is an example. “I don’t do it for the money,” Trump declares. “I’ve got enough, much more than I’ll ever need. I do it to do it. Deals are my art form. Other people paint beautifully on canvas or write wonderful poetry. I like making deals, preferably big deals. That’s how I get my kicks.” Schwartz now laughs at this depiction of Trump as a devoted artisan. “Of course he’s in it for the money,” he said. “One of the most deep and basic needs he has is to prove that ‘I’m richer than you.’ ” As for the idea that making deals is a form of poetry, Schwartz says, “He was incapable of saying something like that—it wouldn’t even be in his vocabulary.” He saw Trump as driven not by a pure love of dealmaking but by an insatiable hunger for “money, praise, and celebrity.” Often, after spending the day with Trump, and watching him pile one hugely expensive project atop the next, like a circus performer spinning plates, Schwartz would go home and tell his wife, “He’s a living black hole!”

Schwartz reminded himself that he was being paid to tell Trump’s story, not his own, but the more he worked on the project the more disturbing he found it. In his journal, he describes the hours he spent with Trump as “draining” and “deadening.” Schwartz told me that Trump’s need for attention is “completely compulsive,” and that his bid for the Presidency is part of a continuum. “He’s managed to keep increasing the dose for forty years,” Schwartz said. After he’d spent decades as a tabloid titan, “the only thing left was running for President. If he could run for emperor of the world, he would.”