On August 7, 1974, a trio of Republican politicians made a sombre journey from Capitol Hill to the White House. Senators Barry Goldwater and Hugh Scott and Representative John Rhodes had dedicated their professional lives to the conservative movement and to the electoral fortunes of the Republican Party. But, on this occasion, they chose to put the interests of their country ahead of the partisan concerns of the G.O.P. They had come to level with Richard Nixon, their fellow-Republican and the President of the United States. The three men told Nixon that the wounds of Watergate had finally cut too deep. His party was abandoning him. It was time for the President to go. He announced his resignation the next day.

The great question in politics today is when, or whether, any Republican will undertake a similar trip to the White House of Donald Trump. Throughout a hundred-plus days, Trump has proved himself temperamentally and intellectually unfit for the Presidency. Following the lamentable campaign of 2016, people surely had modest expectations for the manner in which Trump would conduct himself in office, but his belligerence and his mendacity have been astonishing even by his standards. Still, an undignified Twitter feed, albeit one that originates in the Oval Office, is just a national embarrassment, not a constitutional crisis.

The firing of James Comey, the F.B.I. director, on the other hand, represents not only an abuse of language but an abuse of power. In 1976, Congress, recognizing the political sensitivity of the F.B.I. post, set the director’s term at ten years. This act was partly intended to preclude lengthy tenures like J. Edgar Hoover’s forty-seven-year reign, but also to provide the director with a measure of independence from the incumbent Administration. The law did allow the President to remove the director, but the prevailing norm called for this power to be used sparingly. Before Comey, only one director had been fired, in 1993, when President Clinton dismissed William Sessions for ethical lapses—a decision that generated little dissent.

On Tuesday night, when the news of the firing broke, Administration officials announced that the President had acted, at least in part, because Comey, in the course of clearing Hillary Clinton in last year’s e-mail controversy, had made excessively harsh public comments about her. This was patently absurd; Trump had spent the fall quoting and embracing Comey’s criticisms. Later in the week, Trump contradicted his subordinates’ explanation, telling Lester Holt, of NBC, that he had fired Comey because he was “a showboat” and “a grandstander” (coming from Trump, that sounded more like a projection than like a slight) and because Comey’s leadership had left the F.B.I. “in turmoil,” which it is not.

In fact, during the interview with Holt, Trump all but acknowledged that he had fired Comey because the director had made sure that the Bureau continued to investigate the ties between Trump’s campaign and the efforts by the Russian government and its allies to hand the election to him. This is exactly the kind of investigation that requires the F.B.I. director to have independence; Trump’s short-circuiting of the probe, with Comey’s dismissal, is a grave abuse of Presidential power. The interference in an F.B.I. investigation replicates, with chilling precision, another part of the Watergate story. On June 23, 1972, six days after individuals associated with Nixon’s campaign broke into the Democratic National Committee headquarters, the President and his aide H. R. Haldeman discussed a plan to stop an F.B.I. investigation into the matter. As captured on a White House tape, Nixon told Haldeman that C.I.A. officials “should call the F.B.I. in and say that we wish for the country, don’t go any further into this case—period!” Yet there is one important difference between Nixon’s and Trump’s obstruction of the F.B.I. Nixon had the decency, or at least the deviousness, to do it in secret. Trump, with characteristic brazenness, is conducting his coverup in full view of the public.

In 1974, the release of the June 23rd tape, which became known as the smoking gun, was the final goad to Goldwater and the other Republicans to cease their defense of Nixon and to join calls for his ouster. Trump seems almost to be courting comparisons with Watergate, as when, last Friday, he tweeted the Nixonian threat that Comey “better hope that there are no ‘tapes’ of our conversations.” Trump is not offering explanations; he’s making confessions. The comparison breaks down, however, in that the Republican response to Trump’s lawlessness has ranged from full-throated support to muted statements of concern to, mostly, silence. It is not just that moderate Republicans (and Watergate heroes) like Senators Howard Baker and Lowell Weicker have passed from the Washington scene; it’s that the obsessive partisanship of current leaders like Senator Mitch McConnell and Representative Paul Ryan has stunted the conscience of their entire party. It’s a certainty that history will look unkindly upon the moral blindness of contemporary Republicans.

Only the voters, in 2018 and beyond, will have a chance to send the kind of message that today’s cynical G.O.P. will understand. In the meantime, the Trump Presidency will stagger from one crisis to the next. So far, to the good fortune of the nation—and, even, the world—the President has had to confront disasters only of his own making, like firing Comey and promulgating executive orders that discriminate against religious and ethnic minorities. But, in these perilous and unpredictable times, it’s worth pausing to consider how Trump’s recklessness might manifest itself in a national-security emergency. His default response to conflict has always been to lash out, which can be entertaining on a reality-television show and effective in a political debate. But, as the President of the United States, who commands a nuclear-armed military, Trump is playing for incalculably higher stakes. Democrats, despite their characteristic caution and fecklessness, have begun to speak candidly about Trump, but their status as the minority party renders them nearly irrelevant to Trump’s fate. The Republicans alone have the power to impose limits on this Presidency or to end it altogether. To date, however, no one in the leadership, or even in the rank and file, has displayed the courage to live up to the example set by the honorable Republicans of the past. Daily, and conspicuously, Trump proves the danger of his continued service. His party’s stalwarts won’t be able to say that they weren’t warned. ♦