In this binary tribal world, where everything is at stake, everything is in play, there is no room for quibbles about character, or truth, or principles. If everything — the Supreme Court, the fate of Western civilization, the survival of the planet — depends on tribal victory, then neither individuals nor ideas can be determinative. I watched this play out in real time, as conservatives who fully understood the threat that Mr. Trump posed succumbed to the argument about the Supreme Court. As even Mr. Ryan discovered, neutrality was not acceptable; if you were not for Mr. Trump, then you were for Mrs. Clinton.

The state of our politics also explains why none of the revelations, outrages or gaffes seemed to dent Mr. Trump’s popularity.

In this political universe, voters accept that they must tolerate bizarre behavior, dishonesty, crudity and cruelty, because the other side is always worse; the stakes are such that no qualms can get in the way of the greater cause.

For many listeners, nothing was worse than Hillary Clinton. Two decades of vilification had taken their toll: Listeners whom I knew to be decent, thoughtful individuals began forwarding stories with conspiracy theories about President Obama and Mrs. Clinton — that he was a secret Muslim, that she ran a child sex ring out of a pizza parlor. When I tried to point out that such stories were demonstrably false, they generally refused to accept evidence that came from outside their bubble. The echo chamber had morphed into a full-blown alternate reality silo of conspiracy theories, fake news and propaganda.

And this is where it became painful. Even among Republicans who had no illusions about Mr. Trump’s character or judgment, the demands of that tribal loyalty took precedence. To resist was an act of betrayal.

When it became clear that I was going to remain #NeverTrump, conservatives I had known and worked with for more than two decades organized boycotts of my show. One prominent G.O.P. activist sent out an email blast calling me a “Judas goat,” and calling for postelection retribution. As the summer turned to fall, I knew that I was losing listeners and said so publicly.

And then, there was social media. Unless you have experienced it, it’s difficult to describe the virulence of the Twitter storms that were unleashed on Trump skeptics. In my timelines, I found myself called a “cuckservative,” a favorite gibe of white nationalists; and someone Photoshopped my face into a gas chamber. Under the withering fire of the trolls, one conservative commentator and Republican political leader after another fell in line.