When Mr. Colbert moved to CBS from Comedy Central a year and a half ago, he was the one struggling to adjust. How could he transition from the scathing political comedy of “The Colbert Report” to broadcast TV, where Mr. Fallon had shown, like Jay Leno before him, that audiences just want to escape after a long day?

Mr. Trump has upended that dynamic the way he has so many others. Since his inauguration, there’s no escape. And there’s surprisingly little ratings evidence that people are looking for one. “Late Show” has begun beating “Tonight” in overall viewers. And it’s Mr. Fallon who’s navigating a suddenly foreign environment.

Mr. Colbert is not, right now, the fiercest of the late-night anti-Trumpists (that’s Samantha Bee), the most depthful (John Oliver) or the most potent (Seth Meyers, whose “A Closer Look” segments are killing). But he has a bigger stage, and he seems to have figured out how to be authentic within that space.