As a Presidential candidate, Donald Trump led a charmed existence. Whatever he said, no matter how outrageous, it didn't seem to hurt him. He could insult his Republican opponents, make misogynistic comments about female journalists, call for a ban on Muslims entering the United States, describe Mexican immigrants as rapists and murderers, trot out blatant falsehoods by the dozen, encourage the Russians to hack Hillary Clinton's e-mail account—none of it proved damaging to his candidacy. As he famously remarked, it was as if he could go out and shoot somebody on Fifth Avenue “and I wouldn't lose voters.”

Now things have changed. He might never admit it, but Trump has belatedly discovered a basic principle of politics: words matter. They matter so much, in fact, that they can make or break a Presidency. That's why every one of his predecessors—during the modern era, at least—has chosen his words carefully. It took a few weeks for it to become clear that President Trump, as opposed to candidate Trump, would be subject to this principle. But, at this stage, there can be no doubt about it. Virtually every day brings a fresh example of his own loose words coming back to hurt him.

Take the legal setback to the Administration’s revised travel ban, which was supposed to go into effect on Thursday. Derrick Kahala Watson, the federal judge in Hawaii who, on Wednesday, halted the measure on constitutional grounds, said that the public record “includes significant and unrebutted evidence of religious animus driving the promulgation of the Executive Order.” Among other things, Watson cited a Trump campaign document that said, “Donald J. Trump is calling for a total and complete shutdown of Muslims entering the United States.” On Thursday, another federal judge, Theodore D. Chuang, of Maryland, issued a separate injunction against the revised ban. Citing statements from Trump and his advisers, Chuang said that they indicated the new executive order represented “the realization of the long-envisioned Muslim ban.” (My colleagues Benjamin Wallace-Wells and Jeffrey Toobin have more about both judges’ orders.)

It doesn't stop there. As Slate's Mark Joseph Stern has pointed out, even a staunchly conservative judge who has taken the Administration's side in the fight over the travel bans has criticized some of Trump's public statements. Earlier this week, in a dissent from a Ninth Circuit Court of Appeals ruling against the original ban, Judge Jay Bybee strongly condemned the President’s attacks on James Robart, the district-court judge in Seattle who originally halted the ban. (On Twitter, Trump had referred to Robart as “a so-called judge” and called his ruling “ridiculous.”)

“The personal attacks on the distinguished district judge and our colleagues were out of all bounds of civic and persuasive discourse—particularly when they came from the parties,” Bybee, who worked in the George W. Bush Administration, wrote. “Such personal attacks treat the court as though it were merely a political forum in which bargaining, compromise, and even intimidation are acceptable principles. The courts of law must be more than that, or we are not governed by law at all.”

So far, then, the words that Trump has used to bully and berate the judiciary have succeeded only in encouraging judges to display their independence, with disastrous results for his Administration. And something similar has happened in response to his effort to divert attention from his Russia woes by accusing his predecessor, Barack Obama, of bugging Trump Tower.

Two weeks ago, in a series of early morning tweets, Trump declared that “President Obama was tapping my phones in October, just prior to Election!” Perhaps he thought that no one would interrogate his words. Or perhaps he wasn’t thinking at all. In any case, the White House spokesman Sean Spicer later compounded the error by calling on Congress to investigate Trump's charges. The House and Senate intelligence committees did what Spicer asked, and on Thursday the heads of the Senate committee—the Republican Richard Burr and the Democrat Mark Warner—issued a joint statement that said, “Based on the information available to us, we see no indications that Trump Tower was the subject of surveillance by any element of the United States government either before or after Election Day 2016.”

After that, you might have thought that Trump and his aides would decide to exercise a bit more caution in what they said. Not a bit of it. At his daily briefing on Thursday afternoon, Spicer said that the President “stands by” his bugging accusations. By way of trying to prove that these accusations were reasonable, Spicer also read out some comments made by Andrew Napolitano, a Fox News commentator, in which Napolitano claimed, without citing any evidence, that Obama had asked G.C.H.Q., Britain’s version of the National Security Agency, to bug Trump.

Spicer's briefing created yet more embarrassment for the White House. G.C.H.Q. issued a rare public statement, in which it said that Napolitano's claims were “utterly ridiculous and should be ignored.” In response to reporters' inquiries, a spokesman for Theresa May, the British Prime Minister, repeated the word “nonsense,” and added, “We have made this clear to the administration, and have received assurances that these allegations will not be repeated.” On Friday morning, there were reports, subsequently denied by Trump aides, that the United States had issued a formal apology to Britain.

What can’t be denied is that, yet again, the White House is in the soup. The President and his aides now know that words and truth do matter. Yet they continue to act as if they are oblivious. At a press conference with Angela Merkel, the German Chancellor, on Friday afternoon, a German reporter asked Trump, “Why do you keep saying things you know are not true?” Trump didn't answer directly. When another German reporter asked Trump about the White House citing claims that the British government bugged him, he refused to take responsibility. “We said nothing,” he said. “All we did was quote a certain very talented legal mind who was the one responsible for saying that on television. I didn’t make an opinion on it.” And, once again, Trump refused to back off the discredited claim that Obama bugged him. Looking at Merkel, whose phone the N.S.A. reportedly tapped for years, he said, jokingly, “At least we have something in common, perhaps.”

Of course, it's no joke. But will he ever learn?