The Trumpers (and Stalinists) traded conscience for power; the NeverTrumpers and dissidents chose the reverse. Conscience can be made to suffer, but in the end it usually wins.

That’s why NeverTrumpers matter; why the Trumpers know they matter (which they prove every time they feverishly assert the opposite); and why progressives who dismiss NeverTrumpers as politically irrelevant are wrong. The United States is going to have a right-of-center party in one form or another, and it matters a great deal whether that party is liberal or illiberal, capable or incapable of shame.

Credible conservatives like Charen can still make a positive difference in that respect, in a way that people like, say, Elizabeth Warren cannot. That’s why you want good guys on the other side of the partisan divide, no matter how irrelevant they currently appear to be. When Trumpism fails, as it inevitably will, who will be the Republican Adenauer?

I write this as a parallel contest is taking shape within the Democratic Party, most visibly in the rift between traditional liberals and the social-justice warriors of what used to be the far left. Dianne Feinstein’s failure this week to claim her party’s nomination for the Senate seat she’s held since 1992 is another depressing indication that the rift is widening.

One side believes in the power of reason, the possibility of persuasion, and the values of the Enlightenment. It champions social solidarity for the sake of empowering the individual, rather than creating a society of conformists. It doesn’t see compromise as a dirty word. Its belief in the benefits of civility and diversity does not override its commitment to free speech and independent thought.

As for the other side, it thinks it knows what’s True. It considers compromise knavish. It views debate — beyond its own tightly set parameters — as either pointless or dangerous. And while it sees itself as the antithesis of Trumpism, it is, in its raging intolerance and smug self-satisfaction, Trumpism’s mirror image.

My advice to traditional liberals is not to repeat the establishment Republican mistake of not taking the threat of populist illiberalism seriously, and of not fighting it fiercely. The fabric of an open society is more frayed than most people realize, and it is coming unraveled from more than one end. What happened to the G.O.P. in 2016 could happen to the Democrats in 2020.

The good news, as Charen courageously reminded us, is that these fights should never be abandoned even when they seem lost, and that sometimes the fights most worth having are those with our own side. William F. Buckley and Daniel Patrick Moynihan would have told you the same thing.