There are understandable reasons for his eminence, and he has shown impressive gut-level skill as a campaigner. But he is not deserving of conservative support in the caucuses and primaries. Trump is a philosophically unmoored political opportunist who would trash the broad conservative ideological consensus within the GOP in favor of a free-floating populism with strong-man overtones.

Trump's political opinions have wobbled all over the lot. The real-estate mogul and reality-TV star has supported abortion, gun control, single-payer health care à la Canada, and punitive taxes on the wealthy. (He and Bernie Sanders have shared more than funky outer-borough accents.) Since declaring his candidacy he has taken a more conservative line, yet there are great gaping holes in it.