Esquire had it wrong; Atlantic Monthly had it right.

Leonard Garment's book missed the mark; Ronald Kessler's was on the money.

William Gaines' college journalism class flunked the test; Chase Culeman-Beckman's high-school history paper, although he didn't get an "A" when he turned it in six years ago, should have put him at the head of the class.

A 30-year national guessing game is over: W. Mark Felt, former associate director of the FBI, has revealed to Vanity Fair magazine that he was Deep Throat, the anonymous source who leaked information to The Washington Post about President Nixon's Watergate cover-up.

The Post confirmed on its Web site yesterday that Felt indeed was Deep Throat.

Thus ends one of the nation's longest-running modern-day mysteries.

Felt, it turns out, is the final answer — and not too many had it right. One can rightfully expect in weeks ahead some apologies from those who guessed wrong, and a few "I-told-you-so's" from those who nailed it, including Culeman-Beckman.

Born well after Watergate, Culeman-Beckman was only 8 years old when, he says, Jacob Bernstein, a son of Watergate reporter Carl Bernstein, revealed Deep Throat's identity to him during playtime at summer day camp in 1988.

Except for telling his mom, Culeman-Beckman would keep the secret for nearly 10 years — until spilling the beans in a high-school research paper.

In a 1999 Hartford Courant article about Culeman-Beckman's disclosure (which was printed in The Seattle Times), Felt denied he was Deep Throat. Bernstein said neither he nor reporting partner Bob Woodward had ever told their wives, children or anyone else Deep Throat's identity.

In fact, the two men had agreed not to divulge his identity until after his death. They took pains to exclude any documents identifying him when they sold their Watergate papers two years ago to the University of Texas. And neither, initially, would confirm yesterday that Felt was Deep Throat. By late afternoon, though, Woodward, Bernstein and former Washington Post Executive Editor Ben Bradlee said in an article posted on the paper's Web site that Felt was the anonymous source.

Since Woodward and Bernstein's best-selling book, "All the President's Men," disclosed the existence of Deep Throat, speculation has been rampant, and entire books have been written about his identity.

Some, including the authors of "Silent Coup: The Removal of a President," suspected Alexander Haig, chief of staff under Nixon. Some suspected Nixon adviser David Gergen, whom Esquire magazine in 1976 picked as the No. 1 candidate for Deep Throat.

"Watergate: the Secret Story," a documentary by CBS News and The Washington Post, concluded it was acting FBI director L. Patrick Gray.

Leonard Garment, Nixon's special counsel and author of "In Search of Deep Throat: The Greatest Political Mystery of Our Time," opted for fellow presidential lawyer John Sears.

Fred Fielding, deputy White House counsel to John Dean, was the choice of both Watergate conspirator H.R. Haldeman in his book, "The Ends of Power," and William Gaines' journalism classes at the University of Illinois, which spent four years investigating Deep Throat's identity.

A relative handful of guessers had it right.

Felt was seen as the most likely suspect in "The Bureau: The Secret History of the FBI," a book by Kessler, a former Washington Post reporter; in "Deep Throat: An Institutional Analysis," a 1992 Atlantic Monthly article by James Mann, a former colleague of Woodward's at the Post; and in articles in Washingtonian magazine by its editor, Jack Limpert.

Felt was suspected by the White House, according to the Nixon tapes:

Nixon: "Well, if they've got a leak down at the FBI, why the hell can't Gray tell us what the hell is left? You know what I mean? ... "

Haldeman: "We know what's left, and we know who leaked it."

Nixon: "Somebody in the FBI?"

Haldeman: "Yes, sir. Mark Felt. ... If we move on him, he'll go out and unload everything. He knows everything that's to be known in the FBI. He has access to absolutely everything. ... "

Nixon: "What would you do with Felt? You know what I'd do with him, the bastard? Well that's all I want to hear about it."

Haldeman: "I think he wants to be in the top spot."

Nixon: "That's a hell of a way for him to get to the top."

Felt, in his own memoir, "The FBI Pyramid: Inside the FBI," denied being Deep Throat and said he met with Woodward only once.

The name meant nothing to Culeman-Beckman when he heard it in 1988. Now a graduate student at Cornell University, he could not be reached for comment yesterday.

"I'm 100 percent sure that Deep Throat was Mark Felt," he quoted Bernstein's son as saying. "He's someone in the FBI." He told The Hartford Courant that the boy attributed the information to his father.

After the article, Bernstein, Jacob and his mother, writer and movie director Nora Ephron, all denied that Bernstein had told anyone the identity of "Deep Throat."

To Culeman-Beckman, turnabout was fair play.

"They've been cute about it long enough," Culeman-Beckman said then. "I just think if it's fair of them to dethrone a president, for all intents and purposes, and not tell anyone their source, I don't see why it's not fair for a person like myself to come forward. ... Let the cards fall where they may. There's a chance this could be the answer to one of the greatest political mysteries of our time."

Curiously enough, it was.