Harder sent a similar cease-and-desist letter to Stephen K. Bannon, Trump's former chief strategist who runs the conservative website Breitbart News, alleging that he had defamed the president and violated a nondisclosure employment agreement he had signed with the Trump Organization.
The threats did not appear to work, at least as far as the book is concerned: Wolff and his publisher announced Thursday that publication had been moved forward four days to Friday because of what they described as "unprecedented demand."
But legal experts and historians said the decision by a sitting president to threaten "imminent" legal action against a publishing house, a journalist and a former aide represented a remarkable break with recent precedent and could have a chilling effect on free-speech rights.
Douglas Brinkley, a presidential historian at Rice University, likened Trump's actions this week to those of Richard M. Nixon, whose White House unsuccessfully attempted to stop both the New York Times and The Washington Post from publishing the Pentagon Papers, a secret history of the government's entanglements in Vietnam.
Though several presidents — including Jimmy Carter and Theodore Roosevelt — have sued for libel after leaving office, it is uncommon and potentially damaging for a current occupant of the Oval Office to try to use the powers of the presidency to take on personal and political rivals, Brinkley said.
"Trump is stealing a page out of Richard Nixon's playbook once again," Brinkley said. "When you get criticized by the press or a book that attacks you, you attack back with ferocity. . . . It's a misuse of presidential powers."
But Trump's decision was a deliberate one, according to people who have spoken with him following the publication of excerpts from Wolff's book and who spoke on the condition of anonymity to share candid assessments.
Trump released an initial, lengthy statement Wednesday saying that Bannon had "lost his mind," but he remained dissatisfied, advisers said. The president was especially furious at what he considered several confidences Bannon had betrayed by sharing with Wolff, as well as some alleged falsehoods and exaggerations in the book, and wanted to consult with lawyers who were experts on the topic, one person familiar with his decision said.
Harder had previously represented Trump's wife, Melania, in a dispute with Britian's Daily Mail, as well as son-in-law Jared Kushner, and Trump was eager to retain the lawyer hailed by aides as someone you hire "to crush the media," a White House official said.
Though some White House aides privately worried that mounting such a forceful response was neither presidential nor particularly effective, they also understood that Trump was unlikely to change his mind. "You can debate the strategic effect of what we're doing, but the president was determined to take the legal action," a White House official said.
Although it is incredibly difficult for a public official, especially the president, to prove libel, Harder has experience in taking on media companies. In a lawsuit secretly funded by Silicon Valley venture capitalist Peter Thiel, Harder represented former professional wrestler Hulk Hogan in a successful invasion of privacy case against Gawker Media that resulted in the closure of the company's namesake website. He also briefly represented Hollywood producer Harvey Weinstein, who is facing multiple allegations of sexual harassment.
In an author's note at the beginning of "Fire and Fury," Wolff says that in many instances, he allowed his sources to present conflicting versions of the truth and hopes the reader can judge their veracity, as he has "settled on a version of events I believe to be true."
"Many of the accounts of what has happened in the Trump White House are in conflict with one another," Wolff writes, according to a copy of the book obtained by The Washington Post. "Many, in Trumpian fashion, are baldly untrue."
In the White House's daily news briefing Thursday — which for a second day was largely devoted to disputing questions about the book — press secretary Sarah Huckabee Sanders rejected the suggestion that the letter Trump's legal team sent could be interpreted as a threat by the federal government.
"It's not from the United States government; it's from the president's personal attorney," Sanders said. "And I think it is very clear what its purpose is. And there's nothing to add beyond that."
The president's approach to the claims in Wolff's book, which includes criticism of both him and his family, follows a familiar pattern honed during Trump's time as a combative New York real estate developer.
For nearly half a century, Trump has used lawsuits — and often just the threat of them — as a primary weapon in his arsenal against critics and competitors, deploying libel and slander allegations to push back against those who might embarrass or contradict him. He has had his lawyers threaten book authors, business rivals, attorneys, and critics of his real estate developments and political views.
Competing hotel owners, casino managers and voices in the news media have all found themselves in receipt of sharply worded letters promising legal action that in most cases never happened.
The pattern continued during his presidential campaign. Trump threatened to sue the Times over an article about his alleged unwanted advances on women — but he never did. He threatened to sue the women who said he made the advance — but he never did. And he said during the campaign that he might take action to make it easier to sue journalists — but so far he has not done so.
In one case he did pursue, Trump sued Timothy O'Brien, author of the Trump biography "TrumpNation," on the grounds that the book underestimated Trump's wealth. Trump ultimately lost.
"I think the media generally should stand strong and tall whenever President Trump rattles his saber about lawsuits and intimidation," O'Brien, now the executive editor of Bloomberg View, said Thursday. "He spent decades trying to bully the press, his political opponents, and his business competitors by weaponizing the court system. . . . I think what you're seeing now is the same old Donald Trump, but unfortunately he's able to muster the legal and media artillery of the White House to support his same old insecurities."
Sam Nunberg, a former Trump campaign aide who was later fired, faced a demand for private arbitration from Trump for violating the terms of a confidentiality agreement he'd signed. The two settled, but Nunberg said that even at the time, "my assumption was that he was very, very angry at me."
Nunberg said the president's decision to threaten legal action over Wolff's book likely reflects, as much as anything, his ire over specific remarks Bannon made attacking his family and his business. In the book, Bannon describes a meeting that Trump's oldest son, Donald Trump Jr., and Kushner took during the campaign at Trump Tower with a Russian lawyer as "treasonous" and "unpatriotic," and is quoted as describing Ivanka Trump as "dumb as a brick."
"I don't think the president would have threatened legal action against Steve had Steve not made the comments about Don Jr. or the Trump Organization, which was wrong by Steve to do," Nunberg said.
White House aides were caught ill-prepared when early excerpts of the book leaked Wednesday morning. They had no idea, they said, what Bannon had said to Wolff or that the tome would be so scathing.
The president, who had already begun to sour on his former political strategist, spent the day watching the news unfold on television, complaining about Bannon and soliciting aides and confidants for advice. White House lawyer Ty Cobb, counselor to the president Kellyanne Conway, communications director Hope Hicks, Chief of Staff John F. Kelly and Sanders all huddled with Trump at various points Wednesday.
The White House also called surrogates, urging them to attack Bannon, and publicly and privately argued to reporters that the anecdotes in the book could not be trusted. The president was especially eager to see allies on television blasting his former adviser.
Word quickly spread both inside and outside the White House that people had to choose a side — either Trump, the figurehead of his movement, or Bannon, the self-proclaimed revolutionary who believed he understood Trump's base.
"When it came time and people actually had to decide that for themselves and in a really public way, everyone chose the president," a White House official said.
Marc Fisher, Michael Kranish and Carol D. Leonnig contributed to this report.