Joshua Roberts / Reuters

Donald Trump is intellectually, emotionally, and ethically unsuited for positions of public responsibility. The Atlantic argued this in an editorial published just before the 2016 presidential election, and I tried to document it in more than 150 installments through the election year.

This reality means that for people whose principles date to any era before Trump’s, serving under him brings daily reminders of the impossible choices the great economist Albert O. Hirschman laid out in his book Exit, Voice, and Loyalty. Each day they stay with this regime, they can tell themselves that they are steering events in a less disastrous direction than if they had not been there. And each day they stay with this regime, they are inevitably more compromised and soiled.

Until today, the Trump appointee who had made the best of this doomed predicament was James Mattis, a retired four-star Marine Corps general and Trump’s first secretary of defense. I have known Mattis for decades, have disagreed with him on many points of policy, but have always respected his integrity and independence of intellect and character. In my judgment, he had made two consequential missteps in his long career. One was agreeing, after his retirement from the Marine Corps five years ago, to serve on the board of directors of Theranos, the failed (and apparently fraudulent) blood-testing start-up firm headed by Elizabeth Holmes. The other was his apparent complaisance with Trump’s diktat just before the midterm elections that thousands of U.S. troops deploy to southern Texas to “defend” the United States against the supposed menace of the Central American “caravan.”

We all make mistakes. I’ve made many. And overall, I shared the gratitude many people felt that Mattis—experienced, erudite, with the modest and understated bearing that bespeaks true confidence (and is in the starkest possible contrast to Trump himself)—was in the national-security chain of command, an “adult in the room” serving as a buffer between the impulses of Trump and the actions of the world’s strongest military. He was continuing his service to the nation, its allies, and the world—words I write sincerely, with no air-quotes distance or edge.

And as of today, we know that episodes like the caravan charade were part of Mattis’s long game, the smaller compromises he accepted in order to maintain his important role.

That is over now. Mattis has had enough. Trump put out a preemptive tweet trying to spin Mattis’s departure as “retiring, with distinction.” In fact, it was as pointed a resignation-on-principle by a Cabinet member as we have seen in modern times. “My views on treating allies with respect and also being clear-eyed about both malign actors and strategic competitors are strongly held and informed by over four decades of immersion in these issues,” Mattis wrote. “Because you have the right to a Secretary of Defense whose views are better aligned with yours on these and other subjects, I believe it is right for me to step down from my position.”

The closest thing we have seen to this in the post–World War II era came in 1980, when Cyrus Vance, then the secretary of state, resigned out of disagreement with Jimmy Carter’s approval of a mission to rescue American hostages held in Iran. “You would not be well served in the coming weeks and months by a secretary of state who could not offer you the public backing you need on an issue and decision of such extraordinary importance,” Vance wrote to Carter, “no matter how firm I remain in my support on other issues, as I do, or how loyal I am to you as our leader.” One remarkable aspect of Vance’s statement, at the time, is that he offered it before anyone knew whether the rescue mission would succeed or fail. (It failed, when some rescue helicopters broke down. Vance first delivered his news to Carter in private, before news of the raid came out.) A remarkable aspect of it in retrospect is how careful Vance was to express his respect for Carter’s judgment and leadership on other issues—something Mattis did not even pretend to do, not even with one word.

James Mattis has done his best. He did much better than others of the group Trump once called “my generals.” Unlike H. R. McMaster, he did not give up too much of his pre-Trump reputation. Unlike John Kelly, he did not reveal parts of his character that will lastingly damage his reputation. Unlike Michael Flynn … well, unlike

The onus is not with “my generals” anymore, or with “the adults in the room.” It is with the body that has check-and-balance power over an out-of-control executive.

Donald Trump is dangerous and unfit for office. Nearly every member of the House of Representatives knows this. I bet that every single senator does. History’s eyes are on them, as are the world’s right now. The longer they pretend not to see, the greater the contempt they will earn—and the danger they will invite.

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