To be a prelapsarian conservative in America today — as that creed was understood before 2016 — means getting used to heartbreak. One after another, conservatives that I have admired and respected — Paul D. Ryan, Marco Rubio, Tom Cotton, Bill Bennett, Chris Christie, Newt Gingrich, Scott Walker and many others — have failed the Trump test. They have sacrificed their purported principles to curry favor with a populist demagogue who is turning the Republican Party into the American version of France’s National Front.

The most conspicuous Republican to fall from grace — and he had a long way to fall because he once reached such a lofty pinnacle — is Rudolph W. Giuliani. He has gone, in Joe Scarborough’s biting but accurate phrase, from “America’s mayor” to Trump’s chump. But not even the gaudy, post-9/11 phrase “America’s mayor” can convey the true depth of Giuliani’s achievement, especially to a non-New Yorker.