The official explanation for James Comey’s firing did not survive the night. Aides to President Donald Trump initially claimed that he fired the director of the F.B.I. for mishandling an investigation of Hillary Clinton’s use of a private e-mail server. But that flatly contradicted Trump’s public praise of Comey’s decisions in the Clinton case. Moreover, Trump had repeatedly decried the F.B.I. investigation of his associates for potential collusion with Russia, calling it a “witch hunt,” “FAKE NEWS,” and a waste of money. By nightfall, aides to Trump were conceding to reporters that Trump was infuriated that Comey would not back up his false accusation that President Obama wiretapped him, and that the aides had been trying to “come up with reasons” to justify the firing for more than a week. It emerged that Trump had taken to shouting at the television when he saw reports on the Russia investigation.

Last week, I published a story on the mounting risks to Trump’s Presidency, in which Trump’s friends and Republican strategists told me that the President is increasingly insulated from anyone who can check his impulses. (“Where is the ‘What the fuck’ chorus?” the consultant Steve Schmidt asked.) Comey’s firing confirmed that isolation. Trump has entered a legal and political maelstrom that he does not fully understand. In a sign of his seclusion, he was stunned by the volcanic reaction not only from Democrats but also from Republicans. Richard Burr, the North Carolina Republican who campaigned for Trump and now chairs the Senate Intelligence Committee, which is overseeing the Russia probe, said, “I am troubled by the timing and reasoning of Director Comey’s termination.” Representative Justin Amash, a Michigan Republican who is a member of the conservative House Freedom Caucus, tweeted that he would introduce a bill supporting the creation of an independent commission to investigate Russian involvement in the election.

That Trump believed he could fire the person leading law enforcement’s Russia investigation without a meaningful response from another branch of government is a sign of his unfamiliarity with the separation of powers, and, most perilous to himself, an enduring notion of impunity. Before entering the White House, Trump operated by a principle that, as he put it in a moment of “locker room” candor, “When you’re a star, they let you do it. You can do anything.” The Constitution disagrees, and, by firing Comey and making a baldly contestable claim to his motives, Trump has invited a new investigation into why he took that step, how he described his reasoning, and whether it represents an abuse of office.

This is not the first time that Trump’s words have exposed him to judicial risks that he did not appreciate. In a case that stalled his travel bans against visitors from seven predominantly Muslim countries, a federal judge in Maryland, U.S. District Court Judge Theodore Chuang, ruled that Trump’s campaign comments “include explicit, direct statements of President Trump’s animus towards Muslims and intention to impose a ban on Muslims entering the United States.” Chuang added that Trump’s attempts to disavow those statements could “not wipe them from the ‘reasonable memory’ of a ‘reasonable observer.’ ”

As Congress meets to plot its next steps, several other questions are emerging about the legal and political risks to Trump and his Administration:

Will Comey’s firing kill the Russia investigations—or widen them?

Firing Comey may have accelerated the fire, not extinguished it. It’s easy to compare Trump to Richard Nixon, but another apt comparison lies in the path that brought Bill Clinton to impeachment. The lesson: one investigation leads to another.

Four separate congressional committees are looking into potential collusion, and, several hours before Comey was fired, federal prosecutors told CNN that they had issued grand-jury subpoenas to associates of the former national-security adviser Michael Flynn, requesting business records. The _Times _reported today that Comey had recently asked the Department of Justice for more resources to conduct the Russia investigation. Comey is the third person Trump has fired for investigating his associates’ connections to Russia, including the former acting Attorney General Sally Yates and the former U.S. Attorney Preet Bharara. Representative Adam B. Schiff, the ranking Democrat on the House Intelligence Committee, made clear that he intends to expand his probe into the role that the Attorney General, Jeff Sessions, played in Comey’s firing. Schiff said, “The decision by a President whose campaign associates are under investigation by the F.B.I. for collusion with Russia to fire the man overseeing that investigation, upon the recommendation of an Attorney General who has recused himself from that investigation, raises profound questions about whether the White House is brazenly interfering in a criminal matter.”

Will Republicans in Congress check Trump?

This is the core question: How many members of the Republican caucus find Trump’s over-all approach a threat to their political futures? As early as last month, the approval of the Republican Party had already dropped seven points in three months, to forty per cent. Then Trump pushed for the passage of an unpopular health-care bill, which caused the nonpartisan Cook Report to increase its estimate of the risk that Republicans would lose the House in midterm elections to as high as fifty per cent. How many Republican members of Congress are offended by the news that Trump did not deliver his letter of dismissal through the usual chain of command but dispatched his longtime bodyguard, Keith Schiller, to hand-deliver it to F.B.I. headquarters? How many will conclude, like Amash, of Michigan, that an independent commission, immune to Presidential interference, is the only answer? For men and women who pride themselves on serving the government, the taint of humiliation is becoming harder to justify. As Michael Hayden, the former head of the C.I.A. and the N.S.A., put it, “I’m trying to avoid the conclusion that we’ve become Nicaragua.”

The creation of a special committee, or a special prosecutor, would require that three Republican senators choose to side with forty-eight Democrats, to create a majority. Senator John McCain said that Comey’s firing “only confirms the need and urgency” for a special committee to investigate the 2016 election. In addition to McCain, others are showing growing political reasons to consider that. Jeff Flake, of Arizona, who is up for reëlection in 2018, said, of the Comey decision, “I’ve spent the last several hours trying to find an acceptable rationale for the timing of Comey's firing. I just can’t do it.” But converting that sentiment to action is a step they have not yet taken. For that, it will take public pressure.

How will the public respond?

This part is often overlooked. It should not be. Richard Nixon only resigned because his popularity had dropped so far that congressional Republicans abandoned him. Trump begins at a lower base because he has a lower approval rating than any newly elected President in the history of polling. It is easy to mock nonbinding resolutions by city councils in Los Angeles; Cambridge, Massachusetts; and other liberal provinces that call for a congressional investigation of potentially impeachable offenses.

But these resolutions serve as more than empty symbolism. They are a systematic effort to prime the public and, ultimately, to force members of Congress to introduce a formal resolution (a step that the Democratic leadership has so far avoided). “The more that these communities take these actions calling on their members of Congress to take action, I think there will come a point when one member will break away from the Democratic leadership,” John Bonifaz, the president of Free Speech for People, which is circulating an impeachment petition, told me. “When that happens, it will be hard to put the genie back in the bottle.”