The turn of events has been a stunning reversal of fortune for a man who once operated with such autonomy in the White House that, as chief strategist, he reported only to the president himself.
While the attack on Mr. Bannon may have prompted an unusual expression of contrition from him, the collective force of the attempts to defend the president also ensured that the questions about his mental fitness raised in the book will continue to command attention. This comes as Mr. Trump enters a critical period needing to pass legislation like a spending measure to keep the government open.
The president returned to the White House on Sunday from Camp David, where he had held meetings with Republican leaders in Congress, cabinet officials and senior staff members to set priorities for the year. After an initial message on Twitter that focused on policy matters like border security, the opioid epidemic, infrastructure and the status of young undocumented immigrants, Mr. Trump joined the offensive against the book and the news media coverage of it.
“I’ve had to put up with the Fake News from the first day I announced that I would be running for President,” he wrote on Twitter. “Now I have to put up with a Fake Book, written by a totally discredited author.”
Mr. Bannon has been the target of derision by the president, who has labeled him “Sloppy Steve” and has said he played a far lesser role in Mr. Trump’s political rise than he has been given credit for. Even out of favor, Mr. Bannon has said he remains a champion of the president’s agenda.
But Mr. Miller, the president’s senior policy adviser, acidly criticized Mr. Bannon in an interview on CNN, calling his comments in the book “out of touch with reality,” “vindictive” and “grotesque.”
In a week that held one indignity after another for Mr. Bannon, who has fancied himself a revolutionary poised to tear down the Republican establishment, the words of Mr. Miller may have cut the deepest.
Mr. Miller became a Bannon protégé of sorts during the time Mr. Miller worked for Attorney General Jeff Sessions when Mr. Sessions was in the Senate. He became one of the leading voices on the right calling for tighter controls on legal and illegal immigration.
The two men shared not just a nationalist-tinged conservative view on policy but a desire for political provocation. Mr. Bannon and Mr. Trump were delighted by and cheered on some of Mr. Miller’s more infamous and combative episodes with the news media, like when he chastised a CNN reporter for displaying “cosmopolitan bias” in his understanding of the White House’s immigration positions.
Mr. Miller, however, bristled at the suggestion that he was a Bannon creation, a perception Mr. Bannon himself often encouraged.
Mr. Bannon’s allies understood the White House’s moves this past week to be an act of ruthless political war much like Mr. Bannon himself might have waged during his time in the administration. They said they believed that the president and senior aides like Kellyanne Conway, who is close to Rebekah Mercer, the billionaire who issued a rare statement last week disavowing Mr. Bannon, were sending activists and donors a clear message: He is persona non grata in conservative politics.
Mr. Bannon is not known for second-guessing himself and views apologies as signs of weakness. Nowhere in his statement on Sunday did he actually say he was sorry.
But on Sunday, it was Mr. Miller who had the political leverage. He cast as false the perception that Mr. Bannon had ever played a Svengali-like role in the presidential campaign and the White House.
He said Mr. Bannon’s role had been “greatly exaggerated,” even as the CNN host Jake Tapper ticked off a long list of policies he said Mr. Bannon had played a key role in formulating.
In “Fire and Fury,” Mr. Bannon said Mr. Trump had “lost his stuff,” and Mr. Miller also tried on Sunday to counter the concerns about the president’s mental state. Echoing the president’s own words from Saturday, he called Mr. Trump a “political genius” who could rattle off complete paragraphs on the fly in response to news events and then deliver them “flawlessly” to a campaign audience.
The interview, on the program “State of the Union,” quickly grew heated as Mr. Tapper accused Mr. Miller of being “obsequious” and speaking to an “audience of one.” Before it ended, Mr. Tapper told Mr. Miller that he was wasting his audience’s time.
Mr. Tapper then turned to the camera, even as Mr. Miller was still speaking, and cut to a commercial.
A short time later, the president praised his aide on Twitter, saying that Mr. Miller had “destroyed” Mr. Tapper in the interview.
In addition to assailing Mr. Bannon, Mr. Miller sharply criticized Mr. Wolff and his book, saying it “is best understood as a work of very poorly written fiction.”
Mr. Wolff, appearing on NBC’s “Meet the Press,” stood by the accuracy of his book and contradicted the White House account of how often he had talked to the president.
White House officials said their records showed that Mr. Wolff had last talked to the president in February, but Mr. Wolff said he had talked to the president several times after that. In all, Mr. Wolff said, he talked to the president for about three hours, which also included interviews during the campaign.
He said that Mr. Trump had even initially flattered him about the project, and that he had told interview subjects that “the president said he likes this idea” of a book.
Mr. Wolff also repeated an assertion in the book that many in the White House had talked about the possible invocation of the 25th Amendment, a constitutional provision that permits a president’s powers to be transferred to the vice president when the vice president and a majority of the cabinet or a body created by Congress conclude that the president is incapable of performing his duties.
“This is alarming in every way,” Mr. Wolff said, adding, “This is worse than everybody thought.”
Appearing on Sunday talk shows, others in Mr. Trump’s inner circle dismissed any such worries.
Mike Pompeo, the C.I.A. director, said that he had no concerns about Mr. Trump’s ability to receive and process the kind of intelligence typically presented to presidents, and that Mr. Wolff’s descriptions of Mr. Trump’s mental state were “pure fantasy.”
“I’m with him almost every day,” Mr. Pompeo said on “Fox News Sunday.” “We talk about some of the most serious matters facing America and the world, complex issues. The president is engaged. He understands the complexity. He asks really difficult questions of our team at C.I.A.”
Senator Lindsey Graham, a South Carolina Republican who was briefly a rival to Mr. Trump for the Republican nomination and, until recently, had been a frequent critic of the president, joined his defenders on Sunday.
“I don’t think he’s crazy,” Graham continued. “I think he’s had a very successful 2017. And I want to help him where I can. And we should all want him to be successful. He’s got a lot on his plate.”
With Republican control of the House and possibly the Senate at risk in 2018, Mr. Trump cannot afford another year dominated by news of West Wing dysfunction.
“The reality is people want the president to deliver, and this is a side show,” said Sam Nunberg, a former aide to the Trump campaign who is now close with Mr. Bannon.
Mr. Nunberg added that the president’s disavowals of his former strategist would mean little to voters. “The irony is the president is going to have a rude awakening when numerous candidates during the midterms respectfully decline his offer to campaign with them,” he said.