Yet white evangelical support for Mr. Trump exceeded 80 percent in the 2016 election; he did better even than George W. Bush, who was outspoken about his rebirth through Jesus. Important evangelical figures like Franklin Graham, Billy Graham’s son, practically swoon. “I believe he’s president of the United States for a reason,” Mr. Graham has said of Mr. Trump. “I think God put him there.”

The infatuation appalls some others on the religious right, among them Michael Gerson, a speechwriter for Mr. Bush who was reared in an evangelical family. In an Atlantic magazine article this spring, Mr. Gerson criticized the likes of Mr. Graham and Jerry Falwell Jr. for having provided “religious cover for moral squalor.” A comparably dark assessment was offered by Timothy Keller, a Presbyterian clergyman who wrote in The New Yorker last December, “ ‘Evangelical’ used to denote people who claimed the high moral ground; now, in popular usage, the word is nearly synonymous with ‘hypocrite.’ ”

All the same, Mr. Trump’s us-versus-them pugnacity is well-received by white evangelicals. He shares, and augments, their fear that the country they know is slipping away — if not already lost, what with upheavals like legalized same-sex marriage, acceptance of gay and transgender rights, and the ascension of religious and racial minorities. Those evangelicals, Mr. Gerson wrote, have proved susceptible to “a message of resentful, declinist populism.” In other words, to Mr. Trump’s message.

Thus far, he has delivered for them in significant ways. His two appointments to the Supreme Court signal a desire to chip away at Roe v. Wade, the 1973 decision that legalized abortion. Breaking with decades of precedent, he shifted the United States Embassy in Israel to Jerusalem from Tel Aviv, a move long sought by both Israeli leaders and American evangelicals.

This president seems indifferent at best to social programs long woven into the nation’s cultural fabric but scorned by the religiously orthodox. “Our giveaway programs, our welfarism at home and abroad,” the elder Falwell once sermonized, “is developing a breed of bums and derelicts who wouldn’t work in a pie shop eating the holes out of doughnuts.” One can easily imagine Mr. Trump giving a similar speech.

Will white evangelicals continue to influence the national discourse so powerfully? Perhaps. But the demographic tide would seem to work against them. They are getting older, with a median age of 55. Statistics from the Public Religion Research Institute in Washington show that they now account for 15 percent of the population, down from 23 percent a dozen years ago.

A younger cohort of evangelical Protestants is increasingly black and Latino. Ethnicity aside, they resemble other young Americans in not automatically sharing their elders’ hostility to same-sex marriage, abortion or gay and transgender rights. They are more likely to believe that nurturing the newborn is at least as important as protecting the unborn, and that their self-description as pro-life includes desiring affordable health care for everyone.

In barn-red Texas, some white evangelical women have had it with unquestioned fealty to Republicans. Galvanizing them are Trump administration actions like separating immigrant children from their parents at the southern border, a policy they deem anti-Christian. “I care as much about babies at the border as I do about babies in the womb,” Tess Clarke of Dallas told a New York Times reporter.

For voters who feel as she does, it is a matter of establishing justice. And that, Reinhold Niebuhr might have reminded them were he still living, remains politics’ sad duty.

CLYDE HABERMAN, a regular contributor to Retro Report, has been a reporter, columnist and editorial writer for The New York Times, where he spent nearly 13 years based in Tokyo, Rome and Jerusalem. Subscribe to our newsletter here and follow us on Twitter @RetroReport.

This article first appeared in The New York Times.