Attorneys for the whistleblower who triggered impeachment proceedings against President Trump see the three-decade "Deep Throat" mystery as a model for keeping his identity secret.

The secret of "Deep Throat" was kept from the early '70s until 2005, when former FBI Associate Director Mark Felt came forward at 91 years old. He died two years later.

Whistleblower attorney Mark Zaid, an aficionado of Watergate history, said leaving his client's identity unresolved indefinitely would encourage future whistleblowers. “Our ideal ending is that the identity of the whistleblower is never known and the individual continues on with their personal and professional life as if nothing ever happened," he told the Washington Examiner. "That is the best outcome for most whistleblowers, who simply fulfilled their constitutional duty by reporting a reasonable belief of wrongdoing," he said.

Felt was a prime suspect from the beginning. Eight days before President Richard Nixon resigned in 1974, Washingtonian magazine named him as the probable leaker, though Felt denied it.

Without firsthand sources, the accusation didn't stick. Felt's name was known to the Washington Post journalist he leaked to, Bob Woodward, his reporting partner Carl Bernstein, and their editor Ben Bradlee. It later became known to a prosecutor, but news outlets were left to speculate.

“Even Felt was named in places and his life continued without concern. This may obviously be a very unique situation that sets the precedent for the future,” Zaid told the Washington Examiner. “Basically his identity remained ‘secret’ until he decided otherwise. That was his right."

One man has been identified in news reports as the Ukraine whistleblower: CIA analyst Eric Ciaramella, 33. But definitive confirmation is elusive. Trump says he doesn’t know the name, and well-positioned Capitol Hill sources admit they don't know for sure either.

The whistleblower’s identity is known to Intelligence Community Inspector General Michael Atkinson, who is bound by law to maintain confidentiality. His name likely is known to at least one member of the House Intelligence Committee, Chairman Adam Schiff, since the whistleblower contacted the panel for guidance.

Although public attention has focused on Ciaramella, other names have circulated widely among insiders and on social media.

The whistleblower is a CIA analyst who worked on Ukraine issues at the White House National Security Council, first under President Barack Obama and then briefly under Trump. He lacked firsthand knowledge of his own complaint, which centered on a phone call between Trump and Ukrainian President Volodymyr Zelensky, but key details he provided proved true.

Schiff's committee deposed diplomats and current and former White House staff who confirmed and elaborated on pressure for Ukraine to investigate the whereabouts of a Democratic server and former Vice President Joe Biden and his son Hunter Biden, who worked for a Ukrainian energy firm Burisma. The pressure came as Trump withheld about $400 million in military aid to Ukraine. The phone call includes requests by Trump for Ukraine to investigate the Bidens and Burisma and the circumstances related to the server.

Although Felt's identity remained a secret, he had a complicated post-Watergate career. He left the FBI after 31 years even before Nixon's resignation, accused of leaking. He was convicted in 1980 of warrantlessly surveilling leftist groups but was pardoned by President Ronald Reagan.

The notion that the current whistleblower's true identity could go unknown for decades is unsettling to Republicans who, led by Trump, have demanded the person identify themselves and submit to questioning in Congress. Republicans say the person might have conspired with Schiff to target Trump, and they allege errors in the initial complaint, such as the identity of U.S. officials on the July 25 call and the reason the transcript was placed on a highly secure server.

On Monday, Trump tweeted, "The Whistleblower gave false information & dealt with corrupt politician Schiff. He must be brought forward to testify. Written answers not acceptable!"