President Trump seems uniquely impervious to scandal. While he maintains generally low approval ratings, scandals, such as the infamous “Access Hollywood” tape and “locker room talk,” or even the persistent allegations concerning an affair with porn actress Stormy Daniels, have done little to diminish the robust support that Trump enjoys from his base — white evangelical Christians who are purportedly concerned about morals. A recent poll found that 75 percent of them approved of the president.

But Trump is not the first populist to shrug off bad press. In 18th-century London, there was another politician who, despite his openly scandalous personal life, achieved thunderous political success. John Wilkes was a well-known libertine and an outlaw convicted of seditious libel against the king — and he was tremendously popular. In the 1760s and early 1770s, London regularly resounded with shouts of “Wilkes and Liberty.”

Like Trump, Wilkes possessed a genuine talent for appealing to groups whose core values ought to have been incompatible with his own profligacy.

In Wilkes’s case, this meant the urban middle class. Here was a group that valued respectability, fiscal responsibility, godliness and a restrained sexual ethic. Wilkes, on the other hand, was an outlaw, a chronic debtor who regularly borrowed money from friends and supporters. Once the money arrived, he proceeded to spend extravagantly and rarely repaid the debt. He was a faithful attendee of the established church, but he was also outed as the author of the extremely obscene and utterly sacrilegious parody “An Essay on Woman.” He was a fitting author for the tract, given that he was a sexual libertine who frequented brothels and carried on numerous affairs.

The parallel is striking. Like 18th-century urban middle-class Londoners, conservative American evangelicals also profess to value respectability, thrift, piety and monogamy. Few if any of Trump’s staunchest supporters would claim that his behavior is respectable. He spends lavishly and showily, yet files for bankruptcy with shocking frequency. Throw in his past conduct toward women, and surely the American evangelical ought to be repulsed. ...