David Frum: Donald Trump has been courting right-wing billionaires. He asks: Why would billionaires support such a person? He says the rich would almost certainly pay less taxes if Trump wins.

Frum says the very rich tend to be less informed about what's going on in the world because they live in a social bubble. The danger that Trump represents to U.S. democracy is obvious, he says, but it may not be obvious to some billionaires who think they know more.