In a final plot twist worthy of the saga that Mr. Felt helped to spawn, Vanity Fair magazine released an article from its July issue reporting that Mr. Felt, long a prime suspect to Nixon himself, had in recent years confided to his family and friends, "I'm the guy they used to call 'Deep Throat.' "
Within hours - after Mr. Felt himself, in failing health since suffering a stroke in 2001, appeared in the doorway of his daughter's home in Santa Rosa, Calif. - The Post confirmed his role. He was the official who encouraged its reporters Bob Woodward and Carl Bernstein to follow the trail from the break-in at Democratic National Committee headquarters in the Watergate complex in Washington to the highest levels of the Nixon administration.
Mr. Woodward and Mr. Bernstein initially declined to confirm the Vanity Fair article, believing they had promised Mr. Felt unconditional confidentiality till his death. Meanwhile, The Post, which had guarded the secret as closely as the formula for Coca-Cola, suddenly found itself scrambling to deal with a monthly magazine's scoop of the final footnote to the biggest story in its history.
"It's been The Post's story forever," said Tom Wilkinson, an assistant managing editor of the paper, "and you never like to see those things go to somebody else."
Mr. Felt spent more than 30 years at the Federal Bureau of Investigation, a protégé of its legendary director, J. Edgar Hoover, and was bitterly disappointed after Hoover's death in May 1972 - a month before the Watergate break-in - that Nixon went outside the agency for a new chief. In the past, he repeatedly denied being Deep Throat, and his family said he had been torn about whether to reveal his role and about whether his actions were appropriate for a law enforcement officer.
Indeed, some old Nixon hands like Patrick J. Buchanan, the onetime presidential speechwriter, and G. Gordon Liddy, a convicted Watergate conspirator, reacted to the disclosure of his identity with derision that a top government official would pass word of possible crimes to Mr. Woodward rather than to a prosecutor.
The Post's articles eventually led to Congressional investigations, a special criminal prosecutor, an impeachment inquiry in the House of Representatives and Nixon's resignation in the face of probable conviction by the Senate.
Mr. Felt's grandson Nick Jones, a 23-year-old law student, read a statement on his family's behalf on Tuesday, explaining, "As he recently told my mother, 'I guess people used to think Deep Throat was a criminal, but now they think he's a hero.' " Mr. Jones added that his grandfather believed that "the men and women of the F.B.I. who have put their lives at risk for more than 50 years to keep this country safe deserve more recognition than he."
Mr. Felt later appeared and spoke briefly to reporters, saying: "Hey, look at that. We appreciate you coming out like this."
Deep Throat began life as someone Mr. Woodward described only as "my friend," but he was rechristened by a Post editor in honor of the pornographic film of that name that was then a national sensation. Over the years, the list of possible real-life counterparts for the shadowy figure Hal Holbrook played in the film of Mr. Woodward and Mr. Bernstein's best-selling book, "All The President's Men," has ranged widely - and often improbably - including Henry Kissinger and the first President George Bush, who was then ambassador to the United Nations.
But much of the most serious and informed speculation has long centered on the F.B.I., and on Mr. Felt, who was convicted in 1980 on unrelated charges of authorizing government agents to break into homes secretly, without warrants, in a search for anti-Vietnam War bombing suspects from the radical Weather Underground in 1972 and 1973. Five months later, President Ronald Reagan pardoned him on the grounds that he had "acted on high principle to bring an end to the terrorism that was threatening our nation."
In 1992, on the 20th anniversary of the Watergate break-in, the journalist James Mann cited Mr. Felt as a suspect in an article for The Atlantic Monthly, in which he theorized that Deep Throat's motive was to defend the nation from another kind of threat: to the institutional power, prerogatives and integrity of the F.B.I., which under Hoover had spent decades telling presidents what to do. Suddenly, veterans like Mr. Felt were being told what to do by the Nixon White House, and did not like it.
Mr. Woodward, who did not return telephone calls seeking comment, confirmed as much in comments to The Post's Web site on Tuesday. He said he had decided to confirm his source's identity, despite his concerns that Mr. Felt might not be competent enough to release him from his 33-year-old pledge of confidentiality.
"There's a principle involved," Mr. Bernstein said in a telephone interview from New York, before The Post's confirmation. "Reporters may be going to jail today for upholding that principle, and we don't and won't belittle it now."
The reality may be a bit more complex. The Vanity Fair article, written by a Felt family friend and lawyer, John D. O'Connor, portrays a polite but persistent dialogue between the Felt family and Mr. Woodward in recent years over who should control the rights (and benefits) to such a sensational story.
In encouraging her father to tell his own story, Mr. Felt's daughter, Joan, spoke of the money it might make to help pay tuition bills for her children. For his part, the article says, Mr. Woodward, who has built a lucrative career as a best-selling author, had expressed repeated concerns about whether Mr. Felt, his memory fading and faculties diminished, was really in a position to understand what he was doing.
Told by Mr. Felt's daughter that her father seemed to have unusually clear memories of him, Mr. Woodward, the Vanity Fair article says, simply responded: "He has good reason to remember me."
The Watergate tapes disclosed that Nixon himself had singled out Mr. Felt for special suspicion, once asking his chief of staff, H. R. Haldeman, "Is he a Catholic?" Mr. Haldeman replied that Mr. Felt, who is of Irish descent, was Jewish, and Nixon, who often liked to see Jews at the root of his troubles, replied: "It could be the Jewish thing. I don't know. It's always a possibility."
William D. Ruckelshaus, who resigned as Nixon's deputy attorney general rather than fire the Watergate special prosecutor, Archibald Cox, in 1973, said Tuesday that he had often wondered whether Deep Throat was a composite, simply because of the sheer amount of information he seemed to know about the extent of the Watergate conspiracy.
But Mr. Ruckelshaus noted that Mr. Felt had access to the voluminous F.B.I. interview files, some 1,500 in all, in the agency's investigation into the Watergate affair. "He would see all the agent interviews - they would come through his office - so he would have been privy to an awful lot of information," he said.
Indeed, more than 30 years ago, well before he and Mr. Bernstein had become household names and Deep Throat a legend, Mr. Woodward tantalizingly told the writer Timothy Crouse, in his 1972 campaign book, "The Boys on the Bus," that they had "got somebody at the Justice Department to say, 'Yeah, this whole damn thing is a Haldeman operation,' " directed from the White House, but that the source had said, "We'll never get him and you'll never get him."
In "All The President's Men," Mr. Woodward and Mr. Bernstein paint Deep Throat as a colorful character, steeped in the Washington of an earlier time, "an incurable gossip, careful to label rumor for what it was, but fascinated by it." They added: "He could be rowdy, drink too much, overreach. He was not good at concealing his feelings, hardly ideal for a man in his position. Of late, he had expressed fear for the future of the executive branch, which he was in a unique position to observe."
In the current climate of public skepticism about the use of anonymous sources in journalism, Mr. Woodward and Mr. Bernstein went out of their way in their statement yesterday to note that "many other sources and officials assisted us and other reporters for the hundreds of stories that were written in The Washington Post about Watergate."
But Mr. Bernstein, in a second telephone interview after their confirmation, said: "This is a case history and a case lesson of why it is so important that we have confidential sources. If you were to look back at the original stories, I think hardly any of them had named sources. There's no way this reporting could have been done, nor is there any way that good reporting at a lot of places can be done, without anonymous sources."
At least one prominent Washingtonian expressed a slight nostalgia that the mystery had been solved.
"I mean, I always suspected it, but I never asked," said Sally Quinn, whose husband, Benjamin C. Bradlee, the former executive editor of The Post, was until Tuesday one of only four people publicly known to know the truth. "First of all, I didn't want to be rejected, and I knew he wouldn't tell me. And I knew that if somebody else blabbed, I would get blamed.
Mr. Bradlee himself told The Post that while he had known Deep Throat was a senior F.B.I. official during the investigation, he learned his name only after Nixon resigned.
Ms. Quinn added: "There's been a certain mystique about the story that will not be there any more. Everybody loves a secret that can be kept. Deep Throat has become this living legend, like Camelot. And now it isn't anymore."
