Donald Trump is not incapable of keeping secrets when it serves him to do so. He has guarded years of his tax returns more closely than any president in the modern era. But when the security of the United States, the lives of Western intelligence assets, the trust of U.S. allies, and the fight against ISIS are at stake, he appears to be less adept.

“President Trump revealed highly classified information to the Russian foreign minister and ambassador in a White House meeting last week,” The Washington Post reported Monday, citing revelations from “current and former U.S. officials, who said Trump’s disclosures jeopardized a critical source of intelligence on the Islamic State.”

According to the article, “The information the president relayed had been provided by a U.S. partner through an intelligence-sharing arrangement considered so sensitive that details have been withheld from allies and tightly restricted even within the U.S. government, officials said. The partner had not given the United States permission to share the material with Russia, and officials said Trump’s decision to do so endangers cooperation from an ally that has access to the inner workings of the Islamic State. After Trump’s meeting, senior White House officials took steps to contain the damage, placing calls to the CIA and the National Security Agency.”

National Security Adviser H.R. McMaster, who participated in the meeting, pushed back against the story. “At no time were any intelligence sources or methods discussed, and no military operations were disclosed that were not already known publicly,” he said. But Lawfare persuasively argues that his carefully worded denial is not actually inconsistent with the substance of the Washington Post story.

“This story is false. The president only discussed the common threats that both countries faced,” Dina Powell, a deputy national security adviser, said in a statement.

But unnamed officials—perhaps the same ones—told the same story to reporters at The New York Times and BuzzFeed. The latter news organization added these details to its write-up:

Two US officials who were briefed on Trump’s disclosures last week confirmed to BuzzFeed News the veracity of the Washington Post report, with one noting that “it’s far worse than what has already been reported.”

At least one member of the Senate Intelligence Committee was also briefed on Trump’s disclosures, an intelligence committee staffer said. Sen. Mark Warner, the ranking Democrat on the committee, was not briefed, according to his office. Other members of the committee also said they did not receive a briefing.

Reuters confirmed the story, too. Assuming that the unnamed Washington Post, New York Times, BuzzFeed, or Reuters sources are correct, the episode vindicates various Trump critics.

USA Today’s editorial board argued candidate Trump  was “unfit for the presidency,” observing that he “has demonstrated repeatedly that he lacks the temperament, knowledge, steadiness and honesty that America needs from its presidents.” A flawed temperament, incomplete knowledge, and unsteadiness all contributed to his loose lips with the Russians. As USA Today put it back then, “He speaks recklessly.”

A joint statement signed by numerous Republican foreign-policy experts declared, “Mr. Trump’s own statements lead us to conclude that as president, he would use the authority of his office to act in ways that make America less safe, and which would diminish our standing in the world.” And so it has transpired: he used his authority to handle classified information as he sees fit in a way that made America less safe.

The conservative economist Thomas Sowell warned, “A shoot-from-the-hip, belligerent show-off is the last thing we need or can afford.” Now Trump’s shoot-from-the-hip style and desire to show off U.S. intelligence seems to have done harm.

Ross Douthat cautioned, “I think that reluctant Trump supporters are overestimating the systemic durability of the American-led order, and underestimating the extent to which a basic level of presidential competence and self-control is itself a matter of life and death—for Americans, and for human beings the world over.

And as I wrote just before the election, “Trump didn’t just start off with zero experience in government, itself a worrisome characteristic. He showed that he had neither the discipline nor the respect for the gravity of the job he seeks to study the substance of issues. He just has no idea what he’s talking about on matters from the most basic to the most grave, like what the nuclear triad is and how he’ll manage it. Never in my lifetime and perhaps never in American history has a man with so little knowledge of the issues won a major-party nomination for the presidency.”

All these critiques remain valid. And the way Trump is validating them could have grave political consequences, even though it is almost certainly the case that no laws were broken. As Lawfare writes in its analysis of the Washington Post’s reporting:

This may well be a violation of the President’s oath of office... If the President gave this information away through carelessness or neglect, he has arguably breached his oath of office. As Quinta and Ben have elaborated on in some detail, in taking the oath President Trump swore to “faithfully execute the Office of President of the United States” and to “preserve, protect and defend the Constitution of the United States” to the best of his ability. It’s very hard to argue that carelessly giving away highly sensitive material to an adversary foreign power constitutes a faithful execution of the office of President.

Violating the oath of office does not require violating a criminal statute. If the President decided to write the nuclear codes on a sticky note on his desk and then took a photo of it and tweeted it, he would not technically have violated any criminal law–just as he hasn’t here. He has the constitutional authority to dictate that the safeguarding of nuclear materials shall be done through sticky notes in plain sight and tweeted, even the authority to declassify the codes outright. Yet, we would all understand this degree of negligence to be a gross violation of his oath of office.

Congress has alleged oath violations—albeit violations tied to criminal allegations or breaches of statutory obligations—all three times it has passed or considered seriously articles of impeachment against presidents... Further, two of the three articles of impeachment against Nixon alleged no direct violation of the law. Instead, they concerned Nixon’s abuse of his power as President, which, like the President putting the nuclear codes on Twitter, is an offense that can only be committed by the President and has thus never been explicitly prohibited in criminal law.

There’s thus no reason why Congress couldn’t consider a grotesque violation of the President’s oath as a standalone basis for impeachment—a high crime and misdemeanor in and of itself. This is particularly plausible in a case like this, where the oath violation involves giving sensitive information to an adversary foreign power. That’s getting relatively close to the “treason” language in the impeachment clauses; it’s pretty easy to imagine a hybrid impeachment article alleging a violation of the oath in service of a hostile foreign power. So legally speaking, the matter could be very grave for Trump even though there is no criminal exposure.

For a man like Trump, character is destiny. His glaring lack of mastery over himself and unwillingness to master the knowledge required to do his job well all but guarantee that he will keep damaging America’s interests so long as he remains in office. The most patriotic thing he could do for his country is to grasp his limits and resign.