And a former CIA official wrote in the New York Post that the whistleblower had to be a law professor and not an intelligence official because — wait for it — the complaint included “detailed footnotes.”

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No one expects his anonymity to last as long as Deep Throat’s did.

Richard Nixon became the only president in American history to resign in 1974. It wasn’t until 2005 that W. Mark Felt, the associate director of the FBI during Watergate, revealed he was the one who provided crucial information to Washington Post reporters Woodward and Bernstein during their investigation into the Watergate break-in and coverup.

Thus ended decades of speculation in bars, law schools and late-night tabloid shows, where Deep Throat was fingered as Supreme Court Chief Justice William H. Rehnquist; Secretary of State Henry Kissinger; Nixon speechwriter Pat Buchanan; a composite of several people; and even journalist Diane Sawyer, who was once an assistant in Nixon’s White House press office.

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Perhaps if Twitter had existed in those years, the matter would have been resolved sooner, because there was someone who knew who Deep Throat was, and that someone was a) a master of brevity and wit, b) married to Bernstein for a time and c) eager to blab to anyone who would listen about Felt.

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But no one believed her.

That someone was Nora Ephron, the filmmaker behind classic romantic comedies like “When Harry Met Sally,” “Sleepless in Seattle” and “You’ve Got Mail.”

Before she became beloved by witty women the world over, Ephron was married to Bernstein for four years, from 1976 to 1980. As she recounted later, Bernstein refused to reveal Deep Throat’s identity to her. But she learned that before The Post’s managing editor Howard Simons gave the source the pornographic moniker “Deep Throat,” Woodward had referred to the source as “M.F.” in his notes.

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Woodward always insisted that stood for “My Friend,” but Ephron didn’t believe him, correctly guessing the initials stood for “Mark Felt.” When she confronted Bernstein with her conclusion, he denied it.

Years later, Woodward admitted to NBC News that using “M.F.” was “not very good trade craft on my part.”

In fact, as Woodward explained later, he had met Felt by chance before he was even a journalist. Both men had ended up in a White House waiting room when Felt was lower on the chain in the FBI and Woodward was a Navy courier. Woodward struck up a conversation and, over the years, asked Felt for career advice. Eventually, the mentor-mentee relationship changed when Felt came to Woodward to leak information about Watergate.

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In 1979, while Ephron was pregnant with her and Bernstein’s second child, she discovered her husband was having an affair with a mutual friend. The couple divorced. A few years later, Ephron wrote a fictionalized version of the split in the novel “Heartburn”; she later wrote the screenplay for a film based on the book.

Over the years, as Ephron’s reputation for great movies and bluntness grew, she told hundreds of people the truth: her kids, her friends, rooms full of adoring fans.

“If I gave a speech with 500 people, and [someone] asked me, I told them,” she told NPR in 2006. “I told everyone. But no one listened to me. It was very, very, very frustrating … I was like a tree falling in the forest that no one hears.”

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At times, she later wrote, she suffered in non-silence as “unbelievably idiotic ideas of who Deep Throat was were floated by otherwise intelligent people.”

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“Why these people with these ludicrous theories didn’t call me I cannot imagine,” she joked. “I am listed” in the phone book.

Ephron’s son Jacob Bernstein, apparently inheriting his mother’s propensity for indiscretion, also told classmates in grade school what he had overheard from his mom. In 1999, the Hartford Courant ran an article about a 19-year-old college student who claimed Jacob had told him Felt was Deep Throat when the two attended a day camp together a decade earlier.

When the Courant contacted Bernstein, he laughed off his son’s claim, saying he “has not a clue as to the identity of Deep Throat.”

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There was also someone else who denied it: 86-year-old Mark Felt.

“No, it’s not me,” Felt fibbed to the Courant. “I would have done better. I would have been more effective. Deep Throat didn’t exactly bring the White House crashing down, did he?”

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(Felt also denied it to the Wall Street Journal in 1974, cryptically adding that if he were Deep Throat, he obviously wouldn’t admit it.)

But by 2005, he had changed his mind, and revealed all to Vanity Fair.

Fortunately, Ephron, who died of complications from cancer in 2012, lived long enough to be vindicated and to gloat about it in the way only she could.

“All I can say is that this is a huge load off my mind. Mark Felt is Deep Throat,” she said. “Don’t say I didn’t try to tell you.”