It wasn’t quite evening, nor was it Saturday, but within minutes after President Trump fired the FBI director who was investigating Russian meddling in the president’s election last year, the words “Saturday Night Massacre” swept across a stunned capital.

In Washington, especially in the throes of scandals and investigations, each new shock development sparks a search for useful historical analogies. Immediately on Tuesday evening, Democrats and Republicans alike turned to 1973, to the Saturday Night Massacre, when President Richard M. Nixon rattled the nation by firing Archibald Cox, the special prosecutor who had been appointed to investigate his behavior in the Watergate scandal. On one evening that October, Nixon abolished the office of the special prosecutor, and both the attorney general, Elliot Richardson, and his deputy, William Ruckelshaus, resigned after refusing Nixon’s demand that they fire Cox.

[Here’s how unusual it is to fire an FBI director]

Trump’s firing of FBI chief James B. Comey “is a very Nixonian move,” said John Dean, the White House counsel under Nixon. “This could have been a quiet resignation, but instead it was an angry dismissal.”

On television Tuesday night, the faces of all the president’s men popped out of the history books — fuzzy, black-and-white images of the dark figures of the nation’s worst scandal, which ended with Nixon’s resignation on the eve of his inevitable impeachment. On social media, Comey’s firing instantly took its place alongside other unsettling chapters in the history of presidential power — Watergate, to be sure, but also other struggles between FBI directors and presidents, especially at times when the bureau was investigating the president or his aides.

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But the yearning to find comfort in terrible chapters of American history that the country nonetheless survived runs up against Trump’s lifelong desire to be provocative and unpredictable — and against unprecedented allegations in which a president’s campaign stands accused of possible collusion with a foreign adversary.

“Trump is a unique individual who is not bound by the normal strictures of politics, so we don’t know if he’s doing this because he’s unpredictable or because he’s hiding something,” said John A. Farrell, author of “Richard Nixon: The Life,” a new biography. “But the actions he and his top staff have taken certainly mirror those of their counterparts four decades ago, who were clearly hiding something.”

Trump’s brief letter sacking Comey made only one reference to policy, a line of appreciation that the FBI chief told the president “on three separate occasions that I am not under investigation.” In his memo recommending Comey’s removal, Trump’s new deputy attorney general, Rod J. Rosenstein, did not mention the FBI’s investigation of Russia’s efforts to influence the 2016 presidential election.

[The Justice Department’s case against James B. Comey, annotated]

But much of the reaction from Congress, from Republicans and Democrats alike, focused on that investigation and the need to restore public confidence in the rectitude of the FBI and law enforcement.

Presidents who have been on edge about FBI investigations of their actions have sometimes pushed back hard, but more often they have stepped away from any direct effort to halt a probe.

Nixon’s relationship with the FBI’s first and most iconic director, J. Edgar Hoover, was particularly fraught, and in 1971, the president summoned Hoover, who had led the bureau and its first incarnation since 1924, to the Oval Office to relieve him of his duties.

(Bastien Inzaurralde/The Washington Post)

“Nixon actually called him in for the showdown meeting and just couldn’t do it,” Dean said. “There were talking papers written. It was all set up. They’d been planning it for weeks. And then he chickened out.”

In private discussions with his attorney general, John Mitchell, Nixon said that Hoover “should get the hell out of there.” But at a later meeting with Mitchell, recorded on the White House taping system, Nixon hedged for fear that Hoover might have dirt on him: “We may have on our hands here a man who will pull down the temple with him, including me,” the president said.

In his memoirs, Nixon said that he had been surprised that, as Farrell put it, “the acid of Watergate had dug so deeply into American society that the Saturday Night Massacre would be seen as a great constitutional crisis.”

In 1993, President Bill Clinton also learned how unsettling a confrontation with the FBI could be. Six months after he took office, Clinton fired FBI Director William S. Sessions, saying that his attorney general, Janet Reno, had reported to him that Sessions “can no longer effectively lead the bureau and law enforcement community.”

Asked whether he wanted to get rid of Sessions — a Ronald Reagan appointee — for political reasons, Clinton replied, “Absolutely not.” A Justice Department investigation had found that Sessions had engaged in a pattern of unethical behavior and expense-account padding — garden-variety corruption that might seem almost quaint compared with the Nixon-era crimes. Sessions had used an FBI plane to visit his daughter and an FBI limousine for personal travel, and had a government-paid fence installed at his home.

Sessions said he was a victim of a political vendetta, and he refused Clinton’s entreaties to resign. When Reno, who conducted her own investigation, said Sessions had shown “serious deficiencies in judgment,” Clinton showed him the door.

In retrospect, Clinton lived to regret the change. Louis J. Freeh, a former FBI special agent and U.S. attorney, was a “law enforcement legend,” Clinton said in naming him FBI director. Eight years later, the two men had become mortal enemies. In a 2005 book, Freeh said he was so disgusted by Clinton’s personal scandals that he had stayed until the end of his term only so that Clinton couldn’t appoint his successor.

Freeh had his own problems, including criticism that FBI laxness was among the failings that allowed the September 2001 al-Qaeda attacks; the initial botching of the investigation of the 1996 Olympic Games bombing in Atlanta; and the 2001 arrest of Robert Hanssen, a 25-year FBI veteran, as a longtime Soviet and Russian spy.

But Freeh’s relationship with Clinton — the G-man and the laid-back president — was strained from the start. “The problem was with Bill Clinton — the scandals and the rumored scandals, the incubating ones and the dying ones never ended,” Freeh told “60 Minutes” in 2005. “His closets were full of skeletons just waiting to burst out.”

Freeh blasted Clinton for mishandling the FBI’s investigation of the 1996 Khobar Towers bombing of a U.S. military apartment complex in Saudi Arabia. Clinton, he said, had refused to press the Saudis to allow the FBI to interrogate suspects, even as he hit them up for a contribution to his presidential library.

Former Clinton officials angrily disputed the accusations at the time. “It’s unfortunate he’d stoop to this level in his attempt to rewrite history,” said Clinton spokesman Jay Carson, noting that Freeh had contributed thousands of dollars to Republican politicians.

Freeh’s eventual replacement was scandal-free. Former U.S. attorney and white-collar crime lawyer Robert S. Mueller III took office one week before the al-

Qaeda attacks, and he presided over a wholesale revamp of the bureau’s counterterrorism efforts. When his 10-year term expired, President Barack Obama asked him to stay for two more years. He left in September 2013, replaced by Comey.

As the Watergate analogies poured in from angry and startled politicians Tuesday night, they were accompanied by another echo of the 1970s scandal — calls for the appointment of a special counsel to take over the Russia investigation.

“But remember that until a few hours ago, lots of Democrats were calling for Comey to go,” Farrell said. “That’s being lost in the shuffle as we rush to the Nixonian analogy.”

But the drip-drip-drip nature of Washington scandals is already a primary theme of the Trump presidency. “The question now is how many of these moves by Trump have to happen before we see the shift in public support for the president that happened toward the end of Watergate,” Farrell said.

After Nixon sacked him, Cox, the special prosecutor, defended his decision to conduct the Watergate investigation as he saw fit, rather than yield to the president’s order that he limit his requests for tape recordings of Nixon’s conversations in the White House. “Whether ours shall continue to be a government of laws and not of men is now for Congress and ultimately the American people,” Cox said.

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