Long known for his improvised and volatile stage performances, former President Donald J. Trump now tends to finish his rallies on a solemn note.

Soft, reflective music fills the venue as a hush falls over the crowd. Mr. Trump’s tone turns reverent and somber, prompting some supporters to bow their heads or close their eyes. Others raise open palms in the air or murmur as if in prayer.

In this moment, Mr. Trump’s audience is his congregation, and the former president their pastor as he delivers a roughly 15-minute finale that evokes an evangelical altar call, the emotional tradition that concludes some Christian services in which attendees come forward to commit to their savior.

“The great silent majority is rising like never before and under our leadership,” he recites from a teleprompter in a typical version of the script. “We will pray to God for our strength and for our liberty. We will pray for God and we will pray with God. We are one movement, one people, one family and one glorious nation under God.”

The meditative ritual might appear incongruent with the raucous epicenter of the nation’s conservative movement, but Mr. Trump’s political creed stands as one of the starkest examples of his effort to transform the Republican Party into a kind of Church of Trump. His insistence on absolute devotion and fealty can be seen at every level of the party, from Congress to the Republican National Committee to rank-and-file voters.

Mr. Trump’s ability to turn his supporters’ passion into piety is crucial to understanding how he remains the undisputed Republican leader despite guiding his party to repeated political failures and while facing dozens of felony charges in four criminal cases. His success at portraying those prosecutions as persecutions — and warning, without merit, that his followers could be targeted next — has fueled enthusiasm for his candidacy and placed him, once again, in a position to capture the White House.

‘He’s definitely been chosen by God’

Mr. Trump has long defied conventional wisdom as an unlikely but irrefutable evangelical hero.

He has been married three times, has been repeatedly accused of sexual assault, has been convicted of business fraud and has never showed much interest in church services. Last week, days before Easter, he posted on his social media platform an infomercial-style video hawking a $60 Bible that comes with copies of some of the nation’s founding documents and the lyrics to Lee Greenwood’s song “God Bless the U.S.A.”

But while Mr. Trump is eager to maintain the support of evangelical voters and portray his presidential campaign as a battle for the nation’s soul, he has mostly been careful not to speak directly in messianic terms.

“This country has a savior, and it’s not me — that’s someone much higher up than me,” Mr. Trump said in 2021 from the pulpit at First Baptist Church in Dallas, whose congregation exceeds 14,000 people.

Still, he and his allies have inched closer to the Christ comparison.

Last year, Representative Marjorie Taylor Greene, a Georgia Republican and a close Trump ally, said both the former president and Jesus had been arrested by “radical, corrupt governments.” On Saturday, Mr. Trump shared an article on social media with the headline “The Crucifixion of Donald Trump.”

He is also the latest in a long line of Republican presidents and presidential candidates who have prioritized evangelical voters. But many conservative Christian voters believe Mr. Trump outstripped his predecessors in delivering for them, pointing especially to the conservative majority he installed on the Supreme Court that overturned federal abortion rights.

Mr. Trump won an overwhelming majority of evangelical voters in his first two presidential races, but few — even among his rally crowds — explicitly compare him to Jesus.

Instead, the Trumpian flock is more likely to describe him as a modern version of Old Testament heroes like Cyrus or David, morally flawed figures handpicked by God to lead profound missions aimed at achieving overdue justice or resisting existential evil.

“He’s definitely been chosen by God,” said Marie Zere, a commercial real estate broker from Long Island who attended the Conservative Political Action Conference in February outside Washington, D.C. “He’s still surviving even though all these people are coming after him, and I don’t know how else to explain that other than divine intervention.”

For some of Mr. Trump’s supporters, the political attacks and legal peril he faces are nothing short of biblical.

“They’ve crucified him worse than Jesus,” said Andriana Howard, 67, who works as a restaurant food runner in Conway, S.C.

A political weapon and vulnerability

Mr. Trump’s solid and devoted core of voters has formed one of the most durable forces in American politics, giving him a clear advantage over President Biden when it comes to inspiring supporters.

Forty-eight percent of Republican primary voters are enthusiastic about Mr. Trump becoming the Republican nominee, and 32 percent are satisfied but not enthusiastic with that outcome, according to a recent New York Times/Siena College poll. Just 23 percent of Democrats said they were enthusiastic about Mr. Biden as their nominee, and 43 percent were satisfied but not enthusiastic.

The intensity of the most committed Trump backers has also factored into the former president’s campaign decisions, according to two people familiar with internal deliberations. His team’s ability to bank on voters who will cast a ballot with little additional prompting means that some of the cash that would otherwise be spent on turnout operations can be invested in field staff, television ads or other ways to help Mr. Trump.

But Democrats see an advantage, too. Much of Mr. Biden’s support comes from voters deeply opposed to Mr. Trump, and the president’s advisers see an opportunity to spook moderate swing voters into supporting Mr. Biden by casting Mr. Trump’s movement as a cultlike creation bent on restricting abortion rights and undermining democracy.

Gov. Gavin Newsom of California, a top Democratic ally of Mr. Biden, pointed to an increasingly aggressive online presence from the president’s re-election campaign, which has sought to portray Mr. Trump as prone to religious extremism.

“There’s a huge opportunity here,” Mr. Newsom said in an interview. “Trump is so easily defined, and he reinforces that definition over and over and over again. And Biden has a campaign that can weaponize that now.”

‘Does he really care about evangelicals? I don’t know.’

Mr. Trump’s braiding of politics and religion is hardly a new phenomenon. Christianity has long exerted a strong influence on American government, with most voters identifying as Christians even as the country grows more secular. According to Gallup, 68 percent of adults said they were Christian in 2022, down from 91 percent in 1948.

But as the former president tries to establish himself as the one, true Republican leader, religious overtones have pervaded his third presidential campaign.

Benevolently phrased fund-raising emails in his name promise unconditional love amid solicitations for contributions of as little as $5.

Even more than in his past campaigns, he is framing his 2024 bid as a fight for Christianity, telling a convention of Christian broadcasters that “just like in the battles of the past, we still need the hand of our Lord.”

On his social media platform in recent months, Mr. Trump has shared a courtroom-style sketch of himself sitting next to Jesus and a video that repeatedly proclaims, “God gave us Trump” to lead the country.

The apparent effectiveness of such tactics has made Mr. Trump the nation’s first major politician to successfully separate character from policy for religious voters, said John Fea, a history professor at Messiah University, an evangelical school in Pennsylvania.

“Trump has split the atom between character and policy,” Mr. Fea said. “He did it because he’s really the first one to listen to their grievances and take them seriously. Does he really care about evangelicals? I don’t know. But he’s built a message to appeal directly to them.”

Support from local pastors

Trump rallies have always been something of a cross between a rock concert and a tent revival. When Mr. Trump first started winding down his rallies with the ambient strains, many connected them to similar theme music from the QAnon conspiracy movement, but the campaign distanced itself from that notion.

Steven Cheung, a spokesman for Mr. Trump, said in a statement: “President Trump has used the end of his speeches to draw a clear contrast to the last four years of Joe Biden’s disastrous presidency and lay out his vision to get America back on track.”

But the shift has helped turn Mr. Trump’s rallies into a more aesthetically churchlike experience.

A Trump rally in Las Vegas in January opened with a prayer from Jesus Marquez, an elder at a local church, who cited Scripture to declare that God wanted Mr. Trump to return to the White House.

“God is on our side — he’s on the side of this movement,” said Mr. Marquez, who founded the American Christian Caucus, a grass-roots group.

And at a rally in South Carolina in February, Greg Rodermond, a pastor at Crossroads Community Church, prayed for God to intervene against Mr. Trump’s political opponents, arguing that they were “trying to steal, kill and destroy our America.”

“Father, we have gathered here today in unity for our nation to see it restored back to its greatness,” Mr. Rodermond continued, “and, God, we believe that you have chosen Donald Trump as an instrument in your hands for this purpose.”

But some Christian conservatives are loath to join their brethren in clearing a direct path from the ornate doors of Mar-a-Lago to the pearly gates of Heaven.

Russell Moore, the former president of the Southern Baptist Convention’s public-policy arm, said Mr. Trump’s rallies had veered into “dangerous territory” with the altar-call closing and opening prayers from preachers describing Mr. Trump as heaven-sent.

“Claiming godlike authority or an endorsement from God for a political candidate means that person cannot be questioned or opposed without also opposing God,” Mr. Moore said. “That’s a violation of the commandment to not take the Lord’s name in vain.”