President Donald Trump, Melania Trump, Vice President Mike Pence and Karen Pence at the National Prayer Service on Saturday, Jan. 21. CreditAl Drago/The New York Times

This time a year ago, leaders of the old guard religious right were determined to stop Donald J. Trump from winning the Iowa caucuses. James Dobson, the founder and former president of Focus on the Family, and Tony Perkins, the president of the Family Research Council, joined Senator Ted Cruz as he campaigned in the state. Prominent female anti-abortion activists released an open letter, “Pro-Life Women Sound the Alarm: Donald Trump Is Unacceptable.” It cited, among other things, Mr. Trump’s former ownership of a casino strip club.

Driving around Iowa that January, I heard Christian radio hosts rebuke Jerry Falwell Jr., the president of Liberty University, for giving his support to Mr. Trump.

“Mr. Falwell, in light of Mr. Trump’s attacks on those he happens to dislike at the moment,” asked one, Michael L. Brown, in a plaintive open letter, “How can you point to his Christlike character?”

What a difference a year makes.

Once Mr. Trump seized the Republican nomination, religious conservatives realized that their only path to federal influence lay in a bargain with this profane, thrice-married Manhattan sybarite. So they got in line, ultimately proving to be Mr. Trump’s most loyal backers.

 When, last October, a recording emerged of Mr. Trump’s boasting to a TV host about grabbing women “by the pussy,” many secular conservatives urged him to step aside, but most of the religious right stayed true. Ralph Reed, the founder and chairman of the Faith and Freedom Coalition and head of Mr. Trump’s religious advisory board, argued that for people of faith, “a 10-year-old tape of a private conversation with a TV talk show host ranks pretty low on their hierarchy of their concerns.”

In November, exit polls showed that Mr. Trump won 81 percent of white evangelicals, more than the born-again George W. Bush garnered in either of his races. Mr. Brown, the radio host, remained worried about Mr. Trump’s temperament, but saw the hand of God in his victory.

“I believe Trump has been elected president by divine intervention,” he wrote on Nov. 9.

Mr. Trump is known for failing to honor his debts, but in this case, he’s fully repaying his Christian conservative supporters. For all his flagrant sinfulness, he’s assembling a near-theocratic administration, his cabinet full of avowed enemies of church-state separation. His vice president, Mike Pence, agreed to address the March for Life in Washington, D.C., on Friday, becoming the highest administration official ever to appear at the annual anti-abortion event. And one of Mr. Trump’s first acts as president was to widely expand the so-called global gag rule on abortion.

Past Republican administrations have imposed the rule on foreign organizations receiving American family planning funding, preventing them from discussing abortion with their clients or advocating abortion law liberalization. But George W. Bush specifically exempted from the rule his H.I.V./AIDS program, which would otherwise have been unlikely to meet its prevention and treatment targets. Mr. Trump, however, went right ahead with an executive order applying the rule to all recipients of American global health aid.

There is a deep irony here. It was the religious right’s weakness, which meant it couldn’t play kingmaker in the primary, that made Mr. Trump’s nomination possible, but his victory has given the movement tremendous new power.

The Christian right has been declared dead many times. Before this election, though, it truly seemed to be staggering toward the grave. According to the Pew Research Center, as of last April, barely a third of Republican voters who attended religious services weekly supported Mr. Trump. He had consistent evangelical support, but it tended to come from less strongly affiliated Christians — people who might identify as born again, but who weren’t connected to the congregations that once formed the building blocks of the religious right, and who didn’t take marching orders from the movement’s leaders.

By winning the primary over the strenuous objections of prominent Christian conservatives, Mr. Trump revealed their diminishing sway. When those same leaders decided to champion him, they had to shrug off everything they’d ever said about the primacy of personal morality in politics. Had he lost, they’d have been utterly discredited.

But Mr. Trump didn’t lose, and now the movement that helped deliver his victory faces a deliverance of its own. President Trump may lack a coherent ideology, but he shares with the religious right a kind of Christian identity politics, a sense that the symbols of Christianity, if not its virtues, deserve cultural precedence. As he said in a speech to the Faith and Freedom Coalition’s Road to Majority conference in June: “We will respect and defend Christian Americans. Christian Americans.”

His personnel choices suggest he meant it. Consider Vice President Pence, a man who regularly tries to make policy obey the dictates of faith. In 2002, he gave a speech on the House floor criticizing public schools for teaching evolution but not creationism, even though creationism “was believed in by every signer of the Declaration of Independence.”

Running for Congress in 2000, Mr. Pence called for federal AIDS funding to be directed to groups that “provide assistance to those seeking to change their sexual behavior,” which many have understood to mean gay-conversion therapy, though a spokesman has said this mischaracterized his intent. When in 2002, then Secretary of State Colin Powell endorsed the use of condoms to prevent sexually transmitted diseases, Mr. Pence argued (falsely) that they offer “very, very poor protection” and decried Mr. Powell’s support for them as “too modern of an answer.” He is, needless to say, a tireless foe of Planned Parenthood: In 2011, when the House voted to defund the family planning provider, the legislation was known as the Pence Amendment.

Among senior members of the incoming administration, Mr. Pence is far from alone in opposing secular modernity. Jeff Sessions, Mr. Trump’s choice for attorney general, has said that the idea of a “wall of separation” between church and state “is not constitutional and is not historical.” He once attacked Justice Sonia Sotomayor for having a “postmodern, relativistic, secular mind-set” that is “directly contrary to the founding of our republic.” During Mr. Sessions’s confirmation hearing, Senator Sheldon Whitehouse, Democrat of Rhode Island, asked about his attitude toward the attorneys who will work for him at the Justice Department: “A secular person has just a good a claim to understanding the truth as a person who is religious, correct?” Mr. Sessions replied, “Well, I’m not sure.”

Ben Carson, whom Mr. Trump has appointed to be secretary of the Department of Housing and Urban Development, is similarly hostile to church-state separation, arguing that in taking God out of government, “secular progressives have succeeded de facto in redefining part of the Constitution.” Betsy DeVos, the president’s pick for education secretary, is a billionaire patron of the Christian right who once described her work on education reform as a way to “advance God’s kingdom.” High on her agenda is redirecting public education funds to religious schools.

Mike Pompeo, now confirmed as C.I.A. director, sees America as a combatant in a religious war with Islam — a view shared by Mr. Trump’s appointee as national security adviser, the retired general Michael T. Flynn. “We will defend our Christian values and American exceptionalism with all our heart,” Mr. Pompeo said at a 2015 “God and Country” rally in Kansas. The battle for those values, he said, is “a never-ending struggle” — never ending, that is, “until the rapture.”

Tom Price, Mr. Trump’s choice for secretary of Health and Human Services, has joined Mr. Pence in co-sponsoring bills granting full legal personhood to zygotes. As a Republican congressman from Georgia, Mr. Price has consistently received a 100 percent rating from the National Right to Life Committee.

The resurrection of the politics of coercive piety will transform American life. Some shifts will happen through legislation. The president has promised to sign a bill defunding Planned Parenthood. He has indicated his backing for the reintroduction of a 2015 bill, the First Amendment Defense Act, which would protect those who discriminate against L.G.B.T. people for religious reasons. Mr. Trump has also promised to pick Supreme Court justices who will overturn Roe v. Wade; women’s constitutional right to an abortion may not survive his presidency.

The Christianization of our government will also occur at an administrative level, just as it did during the Bush era, when the Justice Department’s Civil Rights Rivision was transformed.

“The division is bringing fewer voting rights and employment cases involving systematic discrimination against African-Americans and more alleging reverse discrimination against whites and religious discrimination against Christians,” reported Charlie Savage, then with The Boston Globe (now at The Times), in 2006. Something similar can be expected under Mr. Sessions.

Even agencies that don’t deal directly with issues of faith can be infused with religiosity. HUD, for example, regularly contracts with faith-based organizations; under Mr. Carson, more funds may be channeled through conservative Christian groups, with more latitude for proselytizing in government-funded buildings.

With hindsight, Mr. Trump’s libertinism made him the perfect Trojan Horse for conservative values. Because he’s such an irreligious figure, social issues barely figured in the campaign. Even as Christian conservatives put their faith in Mr. Trump, opponents of the religious right’s agenda — which remains broadly unpopular — could convince themselves that Mr. Trump wouldn’t enact it.

According to a pre-election survey, a slight plurality of Trump supporters, 48 percent, oppose defunding Planned Parenthood. Reporting for Slate after the election, I had the chance to watch a series of focus groups that Planned Parenthood convened with some of those voters. In Phoenix, a 58-year-old woman who was a staunch supporter of Planned Parenthood said she couldn’t imagine that Mr. Trump shared the religious right’s priorities.

“He’s probably paid for a few abortions himself,” she said, provoking a peal of laughter.

Presented with Mr. Pence’s history on reproductive rights, a 54-year-old man in the same focus group expressed astonishment.

“I guess I’ve been living in a bubble,” he said.

The religious right has been elevated to power without having to contest its ideas in an election. Sometimes, a deal with the devil pays off, big league.