On October 8th, the outgoing Republican senator Bob Corker sent a tweet calling the White House “an adult day care center.” Corker then told the Times that President Trump’s recklessness could set the nation “on the path to World War III”; he said that most Senate Republicans shared his concerns, as should “anyone who cares about our nation.” Days later, Gabriel Sherman reported in Vanity Fair on the crisis-level discussions among Trump’s aides about how to contain a President who they fear is “unstable” and “unraveling.” According to Sherman’s reporting, the former chief strategist Steve Bannon warned Trump several months ago that “the risk to his presidency wasn’t impeachment, but the 25th Amendment.” That Amendment to the Constitution provides that the Vice-President and a majority of the Cabinet—or, alternatively, a congressionally appointed body—can determine that the President is “unable to discharge the powers and duties of his office” and remove him.

The removal of Trump using the Twenty-fifth Amendment is the aim of a newly launched social movement composed of mental-health professionals. The group, called Duty to Warn, claims that Donald Trump “suffers from an incurable malignant narcissism that makes him incapable of carrying out his presidential duties and poses a danger to the nation.” On Saturday, the organization held coördinated kickoff events in fourteen cities, where mental-health experts spoke out about Trump’s dangerousness and, in several, took to the streets in organized funereal marches, complete with drum corps.

Dr. John Gartner, the founder of Duty to Warn, told me that the event drew nearly a thousand participants across the country. At the Washington, D.C., event, the group presented an award to Representative Jamie Raskin, a Democrat from Maryland and the sponsor of a bill that the group endorses. H.R. 1987 proposes an “Oversight Commission on Presidential Capacity” that, under the Twenty-fifth Amendment, would serve as the congressionally appointed body for determining whether the President cannot execute the powers and duties of his office owing to mental illness or deficiency.

According to a recent Quinnipiac poll, a majority of American voters now believe that Trump is not “fit to serve as President.” While many lay members of the public have observed Trump’s increasingly erratic and unstable behavior, commentary from mental-health experts about Trump’s mental state was slow to gather steam because of the Goldwater Rule, an ethical principle of the American Psychiatric Association that says that psychiatrists cannot express professional opinions about public figures they have not personally examined. “Because we were silenced by the Goldwater Rule, we failed to warn the public that they were heading over the Niagara Falls,” Gartner said. The Duty to Warn movement now represents an outright rebellion against the yoke of the professional norm.

As I’ve written previously, the A.P.A. adopted the Goldwater Rule after members published harsh assessments of the Republican senator Barry Goldwater’s mental fitness to be President during his 1964 election campaign; the consensus was that these were little more than political opinions dressed up as authoritative psychiatric diagnoses. Earlier this year, in response to members’ questions and discontent about the Goldwater Rule’s application with respect to Trump, the A.P.A. debated the issue and announced that not just diagnoses but any “opinion about the affect, behavior, speech, or other presentation of an individual that draws on the skills, training, expertise, and/or knowledge inherent in the practice of psychiatry” was off limits.

Why cling to—and even expand—the rule in the age of Trump? A growing number of those affiliated with Duty to Warn believe that the Goldwater Rule, which is touted as an ethical rule to protect patients, really serves to protect the guild, even where it conflicts with society’s interests. The psychiatrist John Zinner, a participant in the Duty to Warn movement, thinks the rule is “utterly disingenuous.” He told me of a meeting he attended in March of the Washington Psychiatric Society, where a “high official” of the A.P.A. defended keeping the Goldwater Rule in place, on the theory that if psychiatrists spoke out against Trump the government would retaliate by reducing reimbursements to doctors for psychiatric treatment. “It was really not out of ethical concern,” Zinner said, but, rather, concern for “our pocketbooks.”

Whatever the motivations and fears behind the rule, a taboo has been broken. Numerous Duty to Warn participants contributed essays to a new book, “The Dangerous Case of Donald Trump: 27 Psychiatrists and Mental Health Experts Assess a President,” which just landed on Sunday’s Times best-seller list—a sign of the public’s eagerness to know just how afraid it should be of Trump. Duty to Warn has also announced the formation of the “Twenty-fifth Amendment PAC,” which will raise money for political candidates to run on the very issue of removing Trump via the Twenty-fifth Amendment. “We want to be to the Twenty-fifth Amendment what the N.R.A. is to the Second Amendment,” Gartner said. He believes that fear drives people to the polls, and “what people are most afraid of right now is Donald Trump.”

The formation of the new PAC extends beyond simply advocating that psychiatrists and psychologists should be free to offer opinions on public figures. It pivots explicitly into the territory of political advocacy, organization, and activism—which is certain to remind many in the profession of the very sin that led psychiatrists to adopt the Goldwater Rule in the first place. Gartner said that Trump presents “the greatest psychiatric emergency in the history of the United States, maybe in the history of the world.” “The only psychiatric solution here is a political solution,” he said.

The Goldwater Rule’s namesake led the delegation that was sent, in 1974, to tell President Richard Nixon, in the wake of the Watergate scandal, that he had lost support in Congress and could not avoid impeachment; Nixon resigned the next day. Many appear to have given up on the impeachment of President Trump for the moment. But it’s a real turning point when mental-health professionals are so willing to organize politically, break brazenly with long-standing protocol, and even risk discipline by licensing boards. After this, talk of Trump’s removal under the Twenty-fifth Amendment may not seem so crazy.