Richard Nixon’s firing of the Watergate special prosecutor Archibald Cox during the “Saturday Night Massacre” in October 1973 doesn’t just provide the clearest parallel and precedent for Donald Trump’s frightening decision to dismiss FBI director James Comey while his agency is investigating the president’s campaign for possible collusion with Russia. The Saturday Night Massacre also establishes the clear moral and political standard against which to measure the response of America’s leaders to the Comey firing now.

After Nixon fired him, Cox framed the stakes of his dismissal with searing clarity:  “Whether we shall continue to be a government of laws and not of men is for Congress and ultimately the American people” to decide. In answering that question, some of the nation’s leaders fell into predictable partisanship. But mostly the country’s public- and private-sector leadership—including key figures inside Nixon’s own administration and others who had earlier supported the president—answered Cox’s challenge by uniting to defend the rule of law and demanding that the investigation resume unhindered.

The question today is whether a deeply polarized nation can respond with equal determination to Trump’s ominous assault on democratic accountability, which two legal scholars on Tuesday accurately described as “a horrifying breach of every expectation we have of the relationship between the White House and federal law enforcement.”

Cox’s dismissal was triggered by his demand for full access to White House recordings that ultimately revealed Nixon’s complicity in the cover-up of the Watergate break-in. Nixon wanted to provide just limited summaries of the tapes and allow only conservative Democratic Senator John Stennis of Mississippi to listen to the recordings to verify the summaries’ accuracy.  When Cox rejected those terms, Nixon ordered Attorney General Elliot Richardson to fire him. Richardson famously resigned instead, as did his deputy William Ruckelshaus. Finally, Solicitor General Robert Bork—later Ronald Reagan’s rejected Supreme Court nominee—dropped the axe.

The shock over Nixon’s coup from above hardly dispelled all partisanship. Reagan, then the governor of California, and George H.W. Bush, then chairman of the Republican National Committee, both defended Cox’s firing by likening it to Harry Truman’s dismissal of General Douglas MacArthur for contradicting administration policy during the Korean War. “We cannot have a man in [the] executive branch who does not answer to the head of the executive branch,” Bush said. When Cox testified before the Senate Judiciary Committee shortly after his dismissal, GOP senators Strom Thurmond of South Carolina and Edward Gurney of Florida tried to paint him as a Democratic sympathizer biased against Nixon.

But many other voices rose in bipartisan outrage over Nixon’s assault on the investigation. Those began with Richardson himself, who explained his resignation in a lengthy press conference. “At stake in the final analysis is the very integrity of the governmental processes I came to the Department of Justice to help restore,” he said.

Powerful institutions outside of government swelled the chorus. In the 1972 presidential campaign, the AFL-CIO had tilted toward Nixon by conspicuously remaining neutral between him and Democratic nominee George McGovern. But after the Cox dismissal, its national convention unanimously called for Nixon’s impeachment. The American Bar Association convened an emergency meeting to condemn the firing and its president urged the courts and Congress “to repel the attacks which are presently being made on the … rule of law as we have known it.” The public deluged the White House and Congress with telegrams and phone calls in what one Watergate historian called “the greatest outpouring of electronic protest ever seen.”

Critically, several congressional Republicans added their voices. Moderate Maryland GOP Senator Charles Mathias declared that “it is not right for any institution to investigate or prosecute itself.” Arizona Senator Barry Goldwater, the former GOP presidential nominee, said Nixon’s credibility “had reached an all-time low” and he “may not be able to recover.” The backlash was so fierce that Nixon relented within days and released the tapes Cox had sought.

It was too late. Three days after Nixon fired Cox, the House of Representatives began the formal impeachment process that led to the president’s resignation 10 months later. Trump today does not face comparable legal or political jeopardy. But the Comey firing escalates Trump’s disturbing pattern of seeking to undermine and delegitimize any institution capable of challenging him. The same instinct is apparent in his attacks on the news media; his disparaging of “so-called” judges who rule against him; and his earlier dismissals of acting Attorney General Sally Yates and federal prosecutor Preet Bharara, who were both investigating figures in his orbit. At best, this represents disdain from Trump for the checks and balances that underpin American democracy; at worst, it constitutes active subversion of them.

A few Republicans frequently critical of Trump—among them Senators Jeff Flake of Arizona and Ben Sasse of Nebraska, and Ohio Governor John Kasich—joined virtually all Democrats in raising alarms about Comey’s sudden dismissal. But most GOP leaders issued tepid responses that minimized or obscured the core issue: Trump fired the law-enforcement official leading the investigation into his campaign for possible collusion with a hostile foreign government.

With that decision, Trump made clear his willingness to trample the formal and informal limits that have checked the arbitrary exercise of presidential power through American history. What’s unclear is whether leaders and voters in both parties can summon as much will to defend those limits as they did after Nixon’s Saturday Night Massacre. If Trump can decapitate the FBI inquiry into his campaign without real consequence—such as an irresistible bipartisan demand for an independent counsel to take over the investigation—his appetite for shattering democratic constraints is only likely to grow.