As many people are pointing out, Republicans now trying to distance themselves from Donald Trump need to explain why The Tape was a breaking point, when so many previous incidents weren’t. On Saturday, explaining why he was withdrawing his endorsement, Senator John McCain cited “comments on prisoners of war, the Khan Gold Star family, Judge Curiel and earlier inappropriate comments about women” — and that leaves out Mexicans as rapists, calls for a Muslim ban, and much more. So, Senator McCain, what took you so long?

One excuse we’re now hearing is that the new revelations are qualitatively different — that disrespect for women is one thing, but boasting about sexual assault brings it to another level. It’s a weak defense, since Mr. Trump has in effect been promising violence against minorities all along. His insistence last week that the Central Park Five, who were exonerated by DNA evidence, were guilty and should have been executed was even worse than The Tape, but drew hardly any denunciations from his party.

And even if you consider sexual predation somehow uniquely unacceptable, you have to ask where all these pearl-clutching Republicans were back in August, when Roger Ailes — freshly fired from Fox News over horrifying evidence that he used his position to force women into sexual relationships — joined the Trump campaign as a senior adviser. Were there any protests at all from senior G.O.P. figures?

Of course, we know the answer: The latest scandal upset Republicans, when previous scandals didn’t, because the candidate’s campaign was already in free fall. You can even see it in the numbers: The probability of a House Republican jumping off the Trump train is strongly related to the Obama share of a district’s vote in 2012. That is, Republicans in competitive districts are outraged by Mr. Trump’s behavior; those in safe seats seem oddly indifferent.