Three months from the presidential election, and one day after his running mate promised “specific policy proposals for how we rebuild this country at home and abroad,” Americans find themselves asking whether Donald Trump has called for the assassination of Hillary Clinton.

On Tuesday at a rally in North Carolina, Mr. Trump falsely charged, as he has before, that “Hillary wants to abolish, essentially abolish, the Second Amendment.” Then he added: “If she gets to pick her judges, nothing you can do, folks. Although the Second Amendment people, maybe there is, I don’t know.”

Directly behind him, a supporter’s jaw dropped. Afterward, Mr. Trump’s campaign issued an utterly mystifying statement about the “power of unification,” suggesting that Mr. Trump was referring to the political power of Second Amendment supporters, and was not advocating violence. The National Rifle Association, which has endorsed Mr. Trump, concurred with his statement on Supreme Court justices and did not specifically address the rest of his remarks.

Was it a threat? Mr. Trump’s campaign has been marked by extraordinarily combative rhetoric. At another rally, he said he would like to punch a protester in the face and see him leave “on a stretcher.” His supporters have shouted “kill her” when he mentions Mrs. Clinton. The Republican convention heard cries of “lock her up.” A New Hampshire delegate, Al Baldasaro, called for Mrs. Clinton to “be put in the firing line and shot for treason.”

That comment wound up on the Secret Service’s radar. Mr. Trump’s comment should as well.

Seldom, if ever, have Americans been exposed to a candidate so willing to descend to the depths of bigotry and intolerance as Mr. Trump. That he would make Tuesday’s comment amid sinking poll numbers and a wave of Republican defections suggests that when bathed in the adulation of a crowd, Mr. Trump is unable to control himself.

Just eight years ago, Senator John McCain of Arizona, then the Republican presidential nominee, told a man at a town hall session who said he was “scared” of an Obama presidency that Mr. Obama “is a decent person and a person that you do not have to be scared as president of the United States.”

Twenty minutes later, a woman told Mr. McCain that she couldn’t trust Mr. Obama because “he’s an Arab.” ‘’No ma’am,” Mr. McCain replied. “He’s a decent family man, a citizen, that I just happen to have disagreements with on fundamental issues. And that’s what this campaign is all about.”

Republicans would do well to summon the integrity that Mr. McCain showed in 2008, and not just to give some sense of decency to this ugly campaign. The time has come for Republicans — including Mr. McCain — to repudiate Mr. Trump once and for all.

—The New York Times, Aug. 9, 2016