The interview with Mr. Comey and the weekslong media blitz he plans for his book amount to a remarkable public assault on a sitting president by someone who served at the highest levels of power in the government.
The stakes for both men could hardly be higher. Mr. Comey seems likely to be the star witness in any obstruction of justice case brought against the president by Robert S. Mueller III, the special counsel in the sprawling Russia investigation. Mr. Trump’s legal fate, as well as his political fortunes in Washington, may depend on whether he succeeds in undermining the credibility of Mr. Comey and the law enforcement institutions he views as arrayed against him.
The ABC interview, conducted by its chief anchor, George Stephanopoulos, is Mr. Comey’s first major attempt to prevent that from happening, and in it he speaks with the abandon of a man who finally feels unleashed. But Mr. Comey’s liberation is all the more combustible because it is aimed directly at a president who has said with pride on Twitter that “when someone attacks me, I always attack back…except 100x more.”
As if on cue, hours before the interview aired, Mr. Trump called Mr. Comey a “slimeball” for the second time in three days, saying in a pair of early-morning tweets that he belongs in jail for what the president said were lies to Congress and leaks of classified information. In another tweet, Mr. Trump said Mr. Comey would go down in history as “the WORST FBI Director in history, by far!”
Mr. Comey responded later in the day with a more subtle dig of his own.
“My book is about ethical leadership & draws on stories from my life & lessons I learned from others,” he tweeted. “3 presidents are in my book: 2 help illustrate the values at the heart of ethical leadership; 1 serves as a counterpoint.”
It is unclear where the epic battle of wills will lead, other than to a sustained escalation of insults between two men who have each admitted to having outsize egos. But it is certain to be a test of powerful forces in the modern media landscape: the presidential megaphone, amplified by 50 million Twitter followers, and the global reach of an adversary on a seemingly endless, 24-hour, cable-news-driven book tour.
Parts of the interview that have already been aired suggest that Mr. Comey talks in detail about the interactions he had with Mr. Trump, including meetings and phone calls about which he says he meticulously wrote down notes afterward for posterity. (In another tweet on Sunday morning, Mr. Trump said that Mr. Comey’s “‘memos’ are self serving and FAKE!”)
Some of the most startling assertions by Mr. Comey about Mr. Trump in the interview revolve around his first meeting with the president-elect at Trump Tower just days before the inauguration. That day, intelligence officials, including Mr. Comey, briefed the incoming president on Russia’s attempt to meddle with the election.
Mr. Comey says in the interview that Mr. Trump and his aides seemed interested only in what the former F.B.I. director called the “P.R. and spin” about the issue.
“The conversation, to my surprise, moved into a P.R. conversation about how the Trump team would position this and what they could say about this,” Mr. Comey said in a preview of the interview that aired on Sunday morning. “No one, to my recollection, asked: ‘So what’s coming next from the Russians? How might we stop it? What’s the future look like?’”
“It was all, ‘What can we say about what they did and how it affects the election that we just had?’” Mr. Comey said.
It was at the end of the meeting that Mr. Comey says in his book that he asked to speak to Mr. Trump alone to brief him on the salacious “Steele dossier,” which contains unverified allegations about Mr. Trump, including a claim that the Russian government has video recordings of him watching prostitutes urinate on each other in a Moscow hotel room in 2013.
Mr. Comey says in the ABC News interview that Mr. Trump denied the allegations that day, saying, “Do I look like a guy who needs hookers?” Weeks later, in a telephone call from the president after the dossier was published by BuzzFeed, Mr. Trump again denied the account in graphic terms, Mr. Comey said.
“There’s no way I would let people pee on each other around me,” Mr. Trump said, according to Mr. Comey’s account in his book. Mr. Comey said the president also raised the idea that the F.B.I. should investigate the claim as a way of proving that it never happened. Mr. Comey said he warned Mr. Trump that doing so would add to “the narrative” that the president was under investigation.
Mr. Comey said in the interview that it was an “out of body” experience to be talking with the incoming president about whether the incident had taken place, or whether the Russians had material they could use to blackmail Mr. Trump.
“I was floating above myself looking down saying you’re sitting here briefing the incoming president of the United States about prostitutes in Moscow,” Mr. Comey says in the interview. Asked whether he believed Mr. Trump’s denials, Mr. Comey said he was not sure.
“I honestly never thought these words would come out of my mouth, but I don’t know whether the current president of the United States was with prostitutes peeing on each other in Moscow in 2013,” he said. “It’s possible, but I don’t know.”
The president took a break from his attacks on Mr. Comey as he left the White House on a rainy Sunday afternoon to spend time at Trump National Golf Club in Sterling, Va. But it seems likely that he and his allies will not back down in the face of Mr. Comey’s barrage of public accusations, which are expected to continue for weeks.
On ABC’s “This Week” on Sunday, Sarah Huckabee Sanders, the press secretary, unloaded on Mr. Comey, calling him a “self-admitted leaker” and a liar.
For his part, Mr. Comey appears unrelenting as well.
In the book, he compares Mr. Trump’s demands for his loyalty to the induction ceremonies favored by Sammy the Bull, the boss of the Cosa Nostra. Holding little back, Mr. Comey argues that Americans in both parties should be wary of the damage Mr. Trump is doing to the country.
“What is happening now is not normal,” he writes. “It is not fake news. It is not O.K.”