As Trump heads toward the nomination, rural voters are once again the foundation of his support.

In a statement that had all the enthusiasm of a hostage video, Sen. John Thune of South Dakota, a “reasonable” Republican and occasional critic of Donald Trump, endorsed the former president this week. The two other “Johns” angling with Thune to be Republican leader when Sen. Mitch McConnell steps down at the end of the year — Sens. Cornyn of Texas and Barrasso of Wyoming — had already given Trump their support. Thune was late to bend the knee, but bend it he did.

One more prominent Republican lining up behind the party’s inevitable presidential nominee is not shocking news. But the fact that Thune was so clearly reluctant to genuflect before Trump shows that someone like him — a rural-state Republican who’s very conservative, but not a MAGA bomb-thrower — is already an anachronism. In the kind of rural, overwhelmingly white state that Thune represents, Trumpism is the only game in town.