WASHINGTON — W. Mark Felt always denied he was Deep Throat. "It was not I and it is not I," he told Washingtonian magazine in 1974.

It was a denial he maintained for more than 30 years, until yesterday. Throughout that period, he lived with one of the greatest secrets in journalism history and with his own sense of conflict and tension over the role he had played in bringing down a president in the Watergate scandal: Was he a hero for helping the truth come out or a turncoat who betrayed his government, his president and the FBI he revered by leaking to the press?

There were plenty of reasons that he felt such conflict. He was an FBI loyalist in the image J. Edgar Hoover had created for the bureau in its glory days, a career official who lived by the bureau's codes, one of which was the sanctity of an investigation and the protection of secrets. He chased down lawbreakers of all kinds, using whatever means were available to the bureau, and was convicted in 1980 of authorizing illegal break-ins of friends of members of the Weather Underground. He was later pardoned by President Reagan.

But if there were reasons to resist playing the role of anonymous source, there were other motives that drove him to talk. Felt believed that the White House was trying to frustrate the FBI's Watergate investigation and that Nixon was determined to bring the FBI to heel after Hoover's death in May 1972, six weeks before the break-in at the Democratic National Committee's Watergate offices occurred. "From the very beginning, it was obvious to the bureau that a cover-up was in progress," Felt wrote in his 1979 memoir, "The FBI Pyramid."

Felt also may have had a personal motivation to begin talking to Washington Post reporter Bob Woodward. At the time of Hoover's death, he was a likely successor to take over as FBI director. Instead, the White House named a bureau outsider, L. Patrick Gray, then an assistant attorney general, as acting director and leaned on Gray to become a conduit to keep the White House informed of what the FBI was learning.

Felt's identity was revealed with the help of his family in a Vanity Fair article released yesterday. A statement from the family, read by Felt's grandson Nick Jones, described how conflicted he was over whether his role was noble or dishonorable. "Mark had expressed reservations in the past about revealing his identity and about whether his actions were appropriate for an FBI man," Jones said. "But 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.' "

Felt operated during extraordinary times in the country's history and in the history of the bureau. Faced with a rogue White House, an explosive investigation and political pressure that must have been excruciating, he decided to spill secrets anonymously, helping to change the course of history through clandestine nighttime meetings with Woodward in underground parking garages.

Nixon and his White House colleagues during this period were engaged in what the House Judiciary Committee would eventually call a series of criminal acts: obstruction of justice, withholding of material evidence, coercion of witnesses and misuse of the CIA and the Internal Revenue Service.

A secret investigative unit was run from the White House, supported by the CIA and financed by campaign funds, to spy on enemies and to break into a doctor's office in a search for confidential files. Twenty-one participants in what came to be known as the Watergate scandal, including the president's counsel, chief domestic adviser, attorney general and campaign-finance director, pleaded guilty or were convicted of the crimes documented by the FBI and brought to light with Felt's help.

A "very honest" guy

Throughout his career, Felt was seen as a model FBI official. Harry Brandon, who retired from the FBI as deputy assistant for counterintelligence and counterterrorism, recalled making a presentation to Felt as a young agent in the bureau. "He was a tough guy," Brandon said yesterday. "Straight. Very honest. Very straight."

Felt was born in Idaho in 1913. He graduated from the University of Idaho and George Washington University Law School, and joined the FBI in January 1942. He spent World War II in the bureau's espionage section, experience that came into play 30 years later as he set up the series of signals and codes he and Woodward used when they needed to meet one another.

By the early 1970s, as one of the bureau's top officials, he was beginning to demonstrate political independence. At a White House meeting in 1971, he resisted a directive to begin massive wiretaps or lie-detector tests to find the source of leaks about the Nixon administration's national-security strategy.

In March 1972, the Nixon administration was deeply embarrassed by the disclosure of a memo written by a lobbyist at telecommunications giant ITT. It stated that a $400,000 contribution to Nixon's re-election would cause the Justice Department to abandon an antitrust suit against the company.

White House special counsel Charles Colson asked Nixon's personal counsel, John Dean, to obtain an official FBI judgment that the memo was a forgery. Hoover assigned the task of overseeing its inspection to Felt. But Felt reported several days later that the agency's laboratory could not "make a definite finding," a conclusion that undermined the forgery claim, according to Dean's 1976 book, "Blind Ambition."

"Colson, outraged, called Felt to complain. ... He insisted that I persuade Felt to change the [FBI's summary] letter, at least to make it innocuous. Felt would not budge, because the director would not budge," Dean wrote. Felt, in his memoir, confirmed that the bureau had been subjected to "partisan instructions and pressure" in the case.

Yesterday, Colson said he was stunned to learn Felt was Deep Throat, saying he never suspected the FBI official because "he was a professional and that wasn't a professional way to behave."

Shortly after that incident, Hoover died and Felt was passed over to succeed him in favor of Gray. As the Watergate investigation began to unfold, Felt was infuriated by what he saw as Gray's capitulation to the White House. Gray was "sharing all the Bureau's knowledge with the White House staff," he wrote in his memoir.

"For me, as well as for all the Agents who were involved, it had become a question of our integrity," Felt wrote. "We were under attack for dragging our feet, and as professional law-enforcement officers, we were determined to go on."

Haldeman meddles

Within a week of the break-in, the FBI's investigation had begun to develop productive leads; its investigators had figured out that funds to pay the burglars were laundered through a bank account in Mexico City linked to Nixon's re-election effort.

As a result, Nixon's chief of staff, H.R. Haldeman, met with the president June 23 to urge that Vernon Walters, then the CIA's deputy director, tell Gray to "stay the hell out of it" on grounds that it would compromise CIA activities in Mexico, according to a transcript of their conversation.

Gray wanted to do so, Haldeman added, and he just needed an order. "He'll call Mark Felt in, and the two of them — and Mark Felt wants to cooperate because he's ambitious." Nixon replied, "Yeah." Haldeman went on: "He'll call him in and say, 'We've got the signal from across the [Potomac] river to put the hold on this.' "

Later in the conversation, Haldeman sought reassurance that this was the right course of action: "You seem to think the thing to do is get them to stop?" Nixon replied, "Right, fine." Walters met with Gray that day, and according to a Walters memo, Gray told him "this was a most awkward matter to come up during an election year and he would see what he could do."

White House suspicion

None of this was known publicly at the time. But two junior reporters at The Washington Post — Bob Woodward and Carl Bernstein — repeatedly wrote articles that pointed toward White House involvement in the break-in and the subsequent cover-up.

In doing so, they relied heavily on a man they described in their 1974 memoir, "All the President's Men," as "a source in the Executive Branch who had access to information at [the Nixon re-election effort] ... as well as at the White House. He could be contacted only on very important occasions" and asked to confirm information learned elsewhere and provide "perspective." In print, the duo attributed their information only to "sources close to the Watergate investigation."

The leaks infuriated the White House, which pressured Gray into interrogating all the field agents, an act that Felt said had sowed wide resentment. "Numerous times, when Gray was out of the city, John Dean called me, demanding that ... steps be taken to silence the leakers," Felt wrote. "I refused to take such action and frequently I was able to point out to him that some of the leaks could not possibly have come from the bureau."

On Feb. 28, 1973, Nixon and Dean tagged Felt as the potential leaker. He was, Dean told Nixon, "the only person that knows" details such as those being leaked. But Nixon was skeptical. No one would risk his career to become an informant.

According to a tape recording from that day, Nixon said, "You know, suppose that Felt comes out and unwraps the whole thing? What does that do to him? ... He's in a very dangerous situation ... The informer is not wanted in our society. Either way, that's the one thing people do sort of line up against. They ... say, 'well, that (expletive) informed. I don't want him around.' "

Gray was never confirmed as FBI director, and in 1973, William Ruckelshaus was nominated to replace him. Felt clashed repeatedly with his new boss and left the bureau later that year, well before Nixon was to leave office.

Denials

In 1978, Felt was indicted, along with Edward G. Miller, for nine illegal break-ins in New York and New Jersey carried out in 1972 and 1973. When he was arraigned, several hundred FBI agents showed up at the courthouse in a sign of solidarity. The two maintained they had operated within the law, but they were nonetheless convicted in 1980. In April 1981, President Reagan pardoned both men, saying they had served the country with "great distinction."

In his memoir, Felt acknowledged speaking once to Woodward, but in that book and whenever else he was asked, he denied being Deep Throat. In 1999, Felt denied it again to The Hartford Courant after there was another suggestion that he was. "I would have done better," he told the paper. "I would have been more effective." That same summer, Felt told Slate's Tim Noah that it would have been contrary to his responsibilities at the FBI to leak information.