Whoever came up with the phrase “useful idiots” — it’s often credited to Lenin, but there’s no evidence he ever said it — was on to something. There are times when dangerous political movements derive important support from people who will, if these movements achieve and hold power, be among their biggest victims.

Certainly I found myself thinking of the phrase when I read about the Trump fund-raiser held at the Hamptons home of Stephen Ross, chairman of a company that holds controlling stakes in Equinox and SoulCycle.

Most reporting on the Ross event has focused on the possible adverse effects on his business empire: The young, educated, urban fitness fanatics who go to his gyms don’t like the idea that their money is supporting Donald Trump. But the foolishness of Ross’s Trump support goes well beyond the potential damage to his bottom line.

I mean, if you’re a billionaire who also happens to be a racist, supporting Trump makes perfect sense: You know what you’re buying. But if you’re supporting Trump not because of his racism but despite it, because you expect him to keep your taxes low, you’re being, well, an idiot.