At his rally in Phoenix on Tuesday night, Donald Trump remarked, of his decision to take on the Presidency, “Most people think I’m crazy to have done this. And I think they’re right.”

A strange consensus does appear to be forming around Trump’s mental state. Following Trump’s unhinged Phoenix speech, James Clapper, the former director of National Intelligence, said on CNN, “I really question his … fitness to be in this office,” describing the address as “scary and disturbing” and characterizing Trump as a “complete intellectual, moral, and ethical void.” Last week, following Trump’s doubling-down on blaming “many sides” for white-supremacist violence in Charlottesville, Senator Bob Corker, a Republican from Tennessee, said that the President “has not yet been able to demonstrate the stability, nor some of the competence, that he needs” to lead the country. Last Friday, Representative Zoe Lofgren, a Democrat from California, introduced a resolution urging a medical and psychiatric evaluation of the President, pointing to an “alarming pattern of behavior and speech causing concern that a mental disorder may have rendered him unfit and unable to fulfill his Constitutional duties.” Lofgren asked, in a press release, “Does the President suffer from early stage dementia? Has the stress of office aggravated a mental illness crippling impulse control? Has emotional disorder so impaired the President that he is unable to discharge his duties? Is the President mentally and emotionally stable?”

The class of professionals best equipped to answer these questions has largely abstained from speaking publicly about the President’s mental health. The principle known as the “Goldwater rule” prohibits psychiatrists from giving professional opinions about public figures without personally conducting an examination, as Jane Mayer wrote in this magazine in May. After losing the 1964 Presidential election, Senator Barry Goldwater successfully sued Fact magazine for defamation after it published a special issue in which psychiatrists declared him “severely paranoid” and “unfit” for the Presidency. For a public figure to prevail in a defamation suit, he must demonstrate that the defendant acted with “actual malice”; a key piece of evidence in the Goldwater case was Fact’s disregard of a letter from the American Psychiatric Association warning that any survey of psychiatrists who hadn’t clinically examined Goldwater was invalid.

The Supreme Court denied Fact’s cert petition, which hoped to vindicate First Amendment rights to free speech and a free press. But Justice Hugo Black, joined by William O. Douglas, dissented, writing, “The public has an unqualified right to have the character and fitness of anyone who aspires to the Presidency held up for the closest scrutiny. Extravagant, reckless statements and even claims which may not be true seem to me an inevitable and perhaps essential part of the process by which the voting public informs itself of the qualities of a man who would be President.”

These statements, of course, resonate today. President Trump has unsuccessfully pursued many defamation lawsuits over the years, leading him to vow during the 2016 campaign to “open up our libel laws so when they write purposely negative and horrible and false articles, we can sue them and win lots of money.” (One of his most recent suits, dismissed in 2016, concerned a Univision executive’s social-media posting of side-by-side photos of Trump and Dylann Roof, the white supremacist who murdered nine black churchgoers in Charleston, South Carolina, in 2015; Trump alleged that the posting falsely accused him of inciting similar acts.)

The left-leaning psychiatric community was shamed by the Fact episode for having confused political objection and medical judgment, and came under pressure from the American Medical Association, whose members had largely supported Goldwater over Lyndon Johnson. The A.P.A. adopted the Goldwater rule in 1973; Dr. Alan Stone, my colleague at Harvard Law School, was at the time the only member of the A.P.A.’s board to oppose the rule, as a denial of free speech “and of every psychiatrist's God-given right to make a fool of himself or herself.” Stone, who has served on the A.P.A.’s appeals board, told me that a few members over the years have been sanctioned or warned for Goldwater-rule violations, but that the A.P.A. eventually gave up enforcing it, because of the difficulty of providing due process to the accused.

The psychoanalyst Justin Frank, a clinical professor at George Washington University, simply resigned from the A.P.A. in 2003 before publishing his book “Bush on the Couch.” He went on to write “Obama on the Couch,” and is now at work on “Trump on the Couch.” Frank says that the Goldwater rule forces psychiatrists to neglect a duty to share their knowledge with fellow-citizens. “I think it’s fear of being shunned by colleagues,” he told me. “It’s not about ethics.” Had he examined Trump, of course, he would be bound by confidentiality not to speak about him. But Frank believes that restraining psychiatrists from speaking about a President based on publicly available information is like telling economists not to speak about the economy, or keeping lawyers from commenting on legal cases in the public eye.

The A.P.A. reaffirmed and arguably expanded the Goldwater rule in March, stating that it applies not only to a “diagnosis” but also to “an 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.” The upshot is the attempted removal of more than thirty-seven thousand A.P.A. members from a key public conversation, during a moment when their knowledge and authority might aid the public in responsibly assessing the President. The other major mental-health professional organization, the American Psychological Association, with double the membership, also reconfirmed its version of the Goldwater rule. The much smaller American Psychoanalytic Association told its more than three thousand members last month to feel free to comment about political figures—a reprieve more symbolic than practical, since many members concurrently belong to the American Psychiatric Association.

Some assume that simply opting out of voluntary membership in a professional organization frees a person to speak. But versions of the Goldwater rule exist in state licensing-board standards for psychologists and physicians. Some states adopt wholesale the American Psychological Association’s ethical principles as their standard of conduct for licensed psychologists, or have provisions warning that physicians can face disciplinary action for violating a professional medical association’s code of ethics. Dr. Leonard Glass, who practices in one such state, Massachusetts, observed last month, in the Boston Globe, that even if nobody has actually lost his or her license for violating the Goldwater rule, “it is not trivial to be reported to your licensing board for an ethics violation.” This restraint on speech may violate the First Amendment, because, by speaking, practitioners stand to attract state censure, not just disapproval by private organizations. (Disclosure: as a lawyer, I have considered a potential lawsuit based on this First Amendment claim.) It is especially odd to see a muzzling of speech about political figures and elected officials when it is routine for mental-health experts in legal cases to offer opinions based on information from files, without an in-person examination—for example, to help assess how dangerous a person is.

A congressional bill introduced in April proposes establishing a commission to oversee “Presidential capacity,” laying down a path that the Twenty-fifth Amendment allows for involuntary removal of a President. Section 4 of that Amendment provides that a congressionally appointed body can determine that the President is “unable to discharge the powers and duties of his office.” Psychiatrists’ participation in this constitutional process will depend on their appetite for professional opprobrium.

After Trump’s “fire and fury” remarks about North Korea, earlier this month, Dr. Bandy Lee, a professor of psychiatry at Yale Medical School, sent her second letter about Trump to all members of Congress, warning that his “severe emotional impediments” pose “a grave threat to international security.” Four colleagues joined her this time, but, she told me, “In the beginning, I was trying to write letters to Congress members and I couldn’t get anyone to sign on, even though nobody disagreed.” Her book, “The Dangerous Case of Donald Trump,” forthcoming in October, collects essays by more than a dozen mental-health experts and makes the case that the Trump Presidency is an emergency that not only allows but may even require psychiatrists to depart from the Goldwater rule. Seeking contributors, Lee was mindful that most colleagues would be nervous walking the tightrope, so she approached prominent writers who might have enough stature to withstand criticism, including Philip Zimbardo, Judith Herman, Robert Jay Lifton, and Gail Sheehy. (Next month, Lee will have a closed meeting with several as-yet-unnamed lawmakers to advise them on how Congress might convene mental-health professionals to review the President’s state of mind.)

Many Presidents in our history appear to have served while managing various forms of mental illness, including depression, anxiety, social phobia, and bipolar disorder. President Ronald Reagan’s staff, for example, worried about signs of dementia. Concerned about Richard Nixon’s paranoia and heavy drinking in his last days in office, his Defense Secretary is claimed to have told the Joint Chiefs to disregard any White House military orders. But Trump is the only President to be the subject of sustained public discussion about his mental competence and fitness for office.

The Constitution contemplates, by virtue of the First Amendment, that we may freely raise concerns about elected officials, and also that in the extreme circumstance envisioned in the Twenty-fifth Amendment, medical professionals would be free to help us understand whether the President can fulfill his duties. If those who know the most are the least free to speak, neither Amendment can function properly. The Goldwater rule was an overreaction to psychiatrists wielding their professional badge to do politics. Today, the profession risks protecting itself from the taint of politics by withholding expertise from a vital public debate—a situation that seems no less irresponsible.