Gordon Sondland’s belated admission during the impeachment hearings last week of a “quid pro quo” offered by President Trump to Ukraine has been hailed as a “John Dean moment,” a reference to the whistleblowing testimony of the White House counsel during the Senate Watergate hearings.

Like Dean during Watergate, as new witness accounts have highlighted contradictions and evasions in his testimony, the ambassador to the European Union has shifted from protecting the president to protecting himself by implicating key players around him. But as in Watergate, the door to Sondland’s bombshell testimony was opened by whistleblowers whose cumulative testimony forced his hand.

The current hearings were triggered by a whistleblower complaint three months ago by an anonymous CIA analyst, whose “hearsay” claims have been substantiated by direct witnesses to the events described — witnesses such as Lt. Col. Alexander Vindman and Fiona Hill, a former top Russia adviser at the National Security Council. The concerns Vindman and Hill reported to the NSC’s lead counsel in July were aired in public testimony last week.

Wrapping up a tumultuous week of hearings, House Intelligence Committee Chairman Adam B. Schiff (D-Calif.) argued that Trump’s withholding of military aid “to an ally at war” to force a Ukrainian investigation of his political rival Joe Biden “is far more serious than a third-rate burglary of the Democratic headquarters” and goes “beyond anything Nixon did.”

But as Republicans clamor for the anonymous whistleblower to testify and continue to intimidate witnesses, the partisan atmosphere and daily drip of revelations also recall Watergate — specifically how the Nixon campaign tried, and ultimately failed, to keep potential witnesses quiet and insulate President Richard M. Nixon from the crisis.

The first whistleblower during Watergate was driven into the hands of prosecutors and attorneys for the Democratic National Committee thanks to a tactical blunder by the Nixon campaign, whose attorneys washed their hands of him as investigators closed in.

While Dean would later reveal the coverup, former FBI agent Alfred Baldwin was the first member of the burglary team to talk. Three weeks after the Watergate arrests, Baldwin agreed to cooperate with prosecutors to avoid indictment and disclosed an earlier break-in at DNC headquarters, during which two phones were bugged.

The bugs had been planted by ex-CIA officer James W. McCord, who was head of security for the Committee to Reelect the President (CRP). The bug targeting DNC Chairman Larry O’Brien was placed on the wrong phone and didn’t work. But from late May to mid-June, McCord directed Baldwin to monitor over 200 intercepted conversations on DNC official Spencer Oliver’s phone. Baldwin was the only witness to those calls, and his typed logs of the conversations were passed to campaign chief and former attorney general John N. Mitchell.

Baldwin eavesdropped on the calls from a seventh-floor room at the Howard Johnson Motor Lodge, overlooking the sixth-floor offices of the DNC across the street. He monitored DNC headquarters from his balcony and observed the early-morning arrests of McCord and the burglary team. Two days after the arrests, Mitchell instructed his campaign deputy, Jeb Magruder, to burn Baldwin’s logs of the DNC intercepts.

McCord warned Baldwin and his attorneys to “keep their mouths shut.” The head of campaign security instructed Baldwin to “say that he worked for McCord Associates,” the consulting firm through which he had been hired, “rather than CRP.” “Use a CRP lawyer” and “plead the Fifth Amendment to questions,” Baldwin was told.

O’Brien filed a $1 million suit against CRP and the burglars. As luck would have it, one of Baldwin’s attorneys was a close friend of O’Brien’s predecessor, John Bailey, and knew his client could be a star witness in the lawsuit. The attorney briefed Bailey on Baldwin’s involvement, prompting the DNC’s lawyer to tell a judge that he believed DNC headquarters had been under electronic surveillance “over a period of days and weeks” before June 17.

This happened 10 days before prosecutors or the FBI heard Baldwin’s story. They and the public thought the burglars’ mission to bug the DNC had failed.

When Baldwin visited Washington with his lawyers on July 5, CRP attorneys “disavowed” him, insisting that “the Committee had nothing to do with the break-in” and, as Baldwin was never officially working for the committee, there would be no money or help forthcoming from the Nixon campaign.

Abandoned by CRP, Baldwin cut a deal with prosecutors later that day, offering his full cooperation in exchange for avoiding prosecution. In subsequent interviews, Baldwin revealed details of the earlier break-in, the intercepted calls monitored on Oliver’s phone and how he had posed as John Bailey’s nephew to get a tour of the DNC from Oliver’s secretary before the second break-in. He also implicated White House security consultant Howard Hunt and CRP counsel Gordon Liddy in the burglary, deepening the involvement of the Nixon campaign.

Senate Watergate Committee investigators later found it “incredible” that CRP’s lawyers had made no serious attempt to stop Baldwin from telling prosecutors what he knew, seemingly unconcerned that Baldwin would tie Hunt and Liddy to the break-in, as long as nobody higher up the chain was implicated.

On Aug. 26, a DNC attorney met secretly with Baldwin and his attorneys, leading to a 26-page memo that gave the full story to the DNC. Two weeks later, O’Brien announced that his phone and Oliver’s had been tapped in an earlier break-in and monitored for three weeks. The secret memo was also leaked to Washington Post reporters Bob Woodward and Carl Bernstein, who reported Baldwin’s story without identifying him. In early October, Baldwin exited the shadows, giving an exclusive interview to the Los Angeles Times.

While the contents of the calls Baldwin monitored were excluded from the Watergate trial due to wiretapping statutes, his testimony implicated McCord, Hunt, Liddy and the CRP in the break-in. After refusing to testify during the trial, McCord then famously wrote a letter to Judge John Sirica that broke the coverup wide open and led Dean to talk.

One month later, Dean revealed to prosecutors that Hunt and Liddy also had been involved in a White House sanctioned break-in before Watergate that targeted Pentagon Papers whistleblower Daniel Ellsberg. When Hunt admitted his role in the Ellsberg break-in, using CIA equipment, another whistleblower realized he had potentially explosive information and stepped forward.

Rob Roy Ratliff, the CIA liaison to the National Security Council, revealed that his White House office had been used by Hunt to pass sealed envelopes to the agency in the year before the break-in. One of the envelopes was addressed to the CIA’s chief psychiatrist and contained sexual gossip on Ellsberg, and a colleague was “shocked and bewildered by the things that Hunt told him he was doing” at the White House.

Like Vindman and Hill today, Ratliff reported his concerns about Hunt’s irregular activity through proper channels. He alerted the CIA director, worried that fresh revelations of Hunt’s links to the agency could prove damaging, as the CIA had insisted it had cut off all support for Hunt before the Ellsberg break-in. But little came of it. The CIA inspector general’s investigation into the incident remains classified and the contents of the other sealed packages Hunt sent to the agency before Watergate remain a mystery. Like the whistleblowers at the NSC today, Ratliff tried to do the right thing, but his revelations were buried, a reminder of why getting the whistleblower complaint to Congress was critical to the current investigation.

Together, the stories of Baldwin and Ratliff show that Watergate whistleblowing went much deeper than White House Counsel John Dean, and that his pivotal testimony came about in part because of other witnesses before him. Baldwin’s decision to talk was a tale of two attorneys on opposite sides of the political spectrum — the CRP attorney who cut him adrift; and his own attorney, a Democrat who found a willing ear at the DNC.

Ostracized as scapegoats by the Nixon campaign, McCord and Baldwin responded with the most damaging and compelling testimony against the government in the opening week of Senate Watergate hearings.

The experiences of the Watergate whistleblowers reflect what we’re seeing in the impeachment inquiry to date — a battle to keep key witnesses silent, with each new layer of testimony smoking out new witnesses, whose cumulative accounts have now revealed a clear picture.