Trump’s implication that gun owners, or “Second Amendment people,” might attack Hillary Clinton if she is elected President was irresponsible in more than just the obvious ways. Photograph by Eric Thayer / Reuters

On Tuesday, in Wilmington, North Carolina, Donald Trump was riffing on the “horrible” prospect of a Hillary Clinton victory when he paused and suggested, with a lift of his eyebrows, that there is a way that his opponent could be stopped. “If she gets to pick her judges, nothing you can do, folks,” Trump said. “Although, the Second Amendment people—maybe there is, I don’t know.”

In the arena, where the crowd appeared to be half-engaged in Trump’s familiar patter, the comment produced little more than a desultory cheer. But, for a second, Trump looked down, as if the full implications of his comment had caught him by surprise. Of those seated behind Trump, only a bearded attendee in a red shirt reacted immediately, looking to his right, mouth agape. His expression asked, as many Americans soon would: Did the Republican nominee just raise the prospect that, if he loses, gun owners could attack a President—or federal judges?

There are several ways that the Trump campaign might have tried to defuse his remark. Last month, after Trump suggested that Russian hackers should seek to obtain Clinton’s e-mails, the candidate went on to explain on Fox News that he was “being sarcastic.” The explanation did little to assuage his critics, but it gave his admirers a way to say that the media was making a fuss out of nothing. Inconveniently, that won’t work in this case. Even joking about attacking a President or a federal judge is grounds for federal investigation, and Trump has made a point of arguing that no candidate should be above the law. Last month, after the F.B.I. recommended that prosecutors not pursue charges against Clinton for using a private e-mail server, Trump condemned “our rigged system that holds the American people to one standard and people like Hillary Clinton to another.” (On Tuesday evening, the Secret Service, which is responsible for protecting Presidential nominees, said only that it "is aware of the comments made earlier this afternoon." The former C.I.A. director Michael Hayden said, "If someone else had said that, outside the hall, he'd be in a police wagon now, with the Secret Service questioning him.”)

Instead, the Trump campaign presented his comment about the Second Amendment as a testament to the “power of unification.” In a statement, Trump’s spokesman Jason Miller said, “Second Amendment people have amazing spirit and are tremendously unified, which gives them great political power. And this year, they will be voting in record numbers, and it won’t be for Hillary Clinton, it will be for Donald Trump.” In one interview after another, Miller maintained that Trump was referring to “voting power,” though it was clear that Trump had been talking about what “Second Amendment people” could do after losing the vote.

For anyone who cares about the future of American politics, the comment represents a dwindling commitment to politics itself, to the notion that, through rhetoric and competition, we might find a common way as a people. Instead, the Republican candidate made a casual nod to the final force of arms. At this stage, so little that Trump says shocks us, but, now and then, it is worth stepping back and regarding the full damage of it all: the wounds to our fading global image of openness and generosity; the stomping on our admiration for intelligence, eloquence, or honesty; and now the blithe contempt for safe and civil government.

For some, the spirit of violence that has crept into the campaign has been difficult to watch without offering a warning. Last month, the Republican National Convention framed the Democratic nominee as a criminal, a traitor, and a cold-blooded schemer, who, in the words of one speaker, is “personally responsible” for the deaths of Americans in Benghazi. After watching the Convention, Chemi Shalev, a veteran Israeli reporter for Haaretz, wrote that “many Republicans conveniently ignore the fact that words can kill.” He continued:

There are enough people with a tendency for violence that cannot distinguish between political stagecraft and practical exhortations to rescue the country by any available means. If anyone has doubts, they could use a short session with Yigal Amir, Yitzhak Rabin’s assassin, who was inspired by the rabid rhetoric hurled at the Israeli prime minister in the wake of the Oslo Accords. After Rabin was gone, the inciters washed their hands and denied responsibility.

As Trump’s words spread, Senator Chris Murphy, of Connecticut, where a troubled young man massacred twenty-six people at Sandy Hook Elementary School, took to Twitter. “This isn’t play,” he wrote. “Unstable people with powerful guns and an unhinged hatred for Hillary are listening to you, @realDonaldTrump.”

Many gun owners I know, especially those who are most passionate about defending the Second Amendment, take pride in reminding others that they are law-abiding. They are responsible for their conduct and for the safe handling and storage of a firearm; they try not to lose their tempers, and to argue their ideas with facts and civility. Trump, in this sense, is harming them; by suggesting that, to use his phrase, “Second Amendment people” would turn to violence because their favored candidate loses an election is an insult to gun owners everywhere. By feeding a caricature, Trump is effectively advancing the case of those who would seek to curtail access to guns. Truly protecting the Second Amendment means identifying those who are misusing it for their own political purposes.

We do not know if Trump’s remark actually endangered Clinton—or if the legal system will hold him responsible for flirting with that prospect. But it is already clear that, by impugning the character of Second Amendment believers, he is harming their cause.