COLORADO SPRINGS, Colo. — The 11 a.m. service at Church for All Nations, a large nondenominational evangelical church in Colorado’s second-largest city, began as such services usually do. The congregation of young families and older couples swayed and sang along to live music. Mark Cowart, the church’s senior pastor, delivered an update on a church mission project.

Then Mr. Cowart turned the pulpit over to a guest speaker, William J. Federer.

An evangelical commentator and one-time Republican congressional candidate, Mr. Federer led the congregation through an hourlong PowerPoint presentation based on his 2020 book, “Socialism — The Real History from Plato to the Present: How the Deep State Capitalizes on Crises to Consolidate Control.” Many congregants scribbled in the notebooks they had brought from home.

“I believe God is pushing the world to a decision-making moment,” Mr. Federer said, building toward his conclusion. “We used to have national politicians that held back the floodgates of hell. The umbrella’s been ripped after Jan. 6, and now it’s raining down upon every one of us. We had politicians that were supposed to certify that — and instead they just accepted it. And, lo and behold, an anti-Christian spirit’s been released across the country and the world.”

Evangelical churches have long been powerful vehicles for grass-roots activism and influence on the American right, mobilized around issues like abortion and gay marriage. Now, some of those churches have embraced a new cause: promoting Donald J. Trump’s false claim that the 2020 election was stolen.

In the 17 months since the presidential election, pastors at these churches have preached about fraudulent votes and vague claims of election meddling. They have opened their church doors to speakers promoting discredited theories about overturning President Joe Biden’s victory and lent a veneer of spiritual authority to activists who often wrap themselves in the language of Christian righteousness.

For these church leaders, Trump’s narrative of the 2020 election has become a prominent strain in an apocalyptic vision of the left running amok.

“What’s going on in our country right now with this recent election and the fraudulent nature of that?” Mr. Cowart, who did not respond to multiple requests for comment, asked in a sermon last year. “What is going on?”

It’s difficult to measure the extent of churches’ engagement in the issue. Research suggests that a small minority of evangelical pastors bring politics to the pulpit. “I think the vast majority of pastors realize there is not a lot of utility to being very political,” said Ryan Burge, an assistant professor of political science at Eastern Illinois University and a Baptist pastor.

Still, surveys show that the belief in a fraudulent election retains a firm hold on white evangelical churchgoers overall, Mr. Trump’s most loyal constituency in 2020. A poll released in November by the Public Religion Research Institute found that 60 percent of white evangelical respondents continued to believe that the election was stolen — a far higher share than other Christian groups of any race. That figure was roughly 40 percent for white Catholics, 19 percent for Hispanic Catholics and 18 percent for Black Protestants.

Among evangelicals, “a high percentage seem to walk in lock step with Trump, the election conspiracies and the vigilante ‘taking back of America,’” said Rob Brendle, the lead pastor at Denver United Church, who recalled that when he criticized some Christians’ embrace of the Jan. 6 attack on the U.S. Capitol in a sermon the Sunday after the riot, he lost about a hundred members of his congregation, which numbered around 1,500 before the pandemic.

He thinks many fellow clergy may share that view. “I think the jury’s still out, but it’s not a fringe,” he said.

Some of the national evangelical figures who supported Mr. Trump during his presidency and his 2020 campaign, like Robert Jeffress of First Baptist Church in Dallas, separated themselves from his insistence that the election was stolen. Franklin Graham, the son of evangelist Billy Graham and the president of Samaritan’s Purse, equivocated. Writing on Facebook the month after the election, Mr. Graham acknowledged Mr. Biden’s victory but said that when Mr. Trump claimed the election was rigged against him, “I tend to believe him.”

Others embraced Mr. Trump’s claims or argued for the preservation of his rule in spite of his loss. Shortly after the election was called for Mr. Biden, Paula White, a Florida televangelist who served as the White House faith adviser during Mr. Trump’s presidency, led a prayer service in which she and others called upon God to overturn the election.

Greg Locke, a preacher who leads the Global Vision Bible Church in Mount Juliet, Tenn., spoke alongside Alex Jones of Infowars at a “Rally for Revival” demonstration in Washington the night before the Jan. 6 attack. Mr. Locke offered a prayer for the Proud Boys, the violent far-right group, and for Enrique Tarrio, the organization’s leader who has since been indicted on charges of conspiracy for his role in the Capitol insurrection.

Mr. Locke — whose congregation is relatively small, but who claims a social media audience in the millions — is one of more than a dozen pastors who have appeared onstage at the ReAwaken America Tour: a traveling roadshow that has featured far-right Republican politicians, anti-vaccine activists, election conspiracists and Trumpworld personalities, including Lt. Gen. Michael Flynn, a central figure in the effort to overturn the election in late 2020.

The event has drawn crowds of thousands of Trump supporters in nine states in the past year. All but one of the tour’s stops have been hosted by megachurches, and the tour is sponsored by a charismatic Christian media company.

The performances wrap the narrative of election fraud in a megachurch atmosphere, complete with worship music and prayer, and have drawn criticism from some Christian clergy. When the tour came to a church in San Marcos, Calif., this month, a local Methodist minister denounced it as an “irreligious abomination” in an opinion essay.

Smaller churches, meanwhile, have proven an important support network for the individual activists who now travel the country promoting the narrative of a stolen election.

“Churches and bars, baby. That’s where it was happening in 1776,” wrote Douglas Frank, a high school math and science teacher in Ohio whose widely debunked analyses of the 2020 results have been influential with election conspiracists, in a Telegram post last month. So far this year, more than a third of the speeches he has promoted on his social media accounts have been hosted by churches or religious groups.

Seth Keshel, a former Army captain and military intelligence analyst who worked alongside Mr. Flynn in the weeks immediately after the election, is a popular draw with the same crowds. He attributed the prevalence of churches on the circuit to the instincts of local organizers.

“Most conservatives are evangelicals and naturally think ‘church’ as a venue,” he wrote in an email. “There are some pastors more fired up about elections and liberty but not all.”

Churches are commonly used as spaces for events they do not directly endorse. Often, though, pastors at the churches hosting these speakers have used their appearances as an occasion to opine about the election to their congregation.

“This will be your opportunity to find out real information about what really happened at the polls,” D.J. Rabe, a pastor of The House Ministry Center, a nondenominational church in Snohomish, Wash., told his congregation at the Sunday worship service before a speaking appearance by Mr. Keshel in August. “Here’s what we’re going to find out: What everyone thinks happened didn’t really happen. The information is coming out.”

The connection between churches and election activists has been particularly visible in Colorado Springs, a longstanding hub of conservative evangelical political power that has lately become a hotbed of the “election integrity” crusade.

The city is home to two particularly active groups dedicated to the cause: the U.S. Election Integrity Plan and F.E.C. United, a right-wing organization that protested Covid lockdowns in early 2020 and later became a prominent promoter of election conspiracies.

Both groups have support from local churches. Church for All Nations has twice hosted talks by U.S. Election Integrity Plan leaders in its sanctuary as part of the church’s current events forum. At the first event, after a woman in the audience said, “I want to see butts in jail!” Ken Davis, a group leader at the church, replied: “I think there’s a certain punishment for treason in this country, and it’s not jail.”

The second event, in March, was held shortly after the regional N.A.A.C.P. chapter and other groups filed a lawsuit against the U.S. Election Integrity Plan. The organization’s volunteers — some of whom were carrying firearms, the lawsuit claims — visited addresses they believed to be potentially associated with fraudulent ballots, asking residents how they voted in the 2020 election. The lawsuit argues that their actions violated both the 1965 Voting Rights Act and the Ku Klux Klan Act of 1871. Holly Kasun, U.S. Election Integrity Plan’s co-founder, called the lawsuit a “baseless claim” in an email.

In February, The Rock, a nondenominational evangelical church in nearby Castle Rock, Colo., hosted F.E.C. United for a talk featuring Shawn Smith, a founder of U.S. Election Integrity Plan, and Tina Peters, the clerk and recorder of Mesa County, who has since been indicted on charges that she devised a scheme to copy voting-machine hard drives and share the data with prominent 2020 election conspiracists. (In a statement, Ms. Peters, who is running for secretary of state in Colorado, maintained her innocence.)

Mr. Smith made headlines when he accused Colorado’s secretary of state, Jena Griswold, of election fraud and told the crowd: “If you’re involved in election fraud, you deserve to hang.” Mike Polhemus, The Rock’s pastor, later distanced the church from the event and told a local TV station that Mr. Smith’s remarks were “inappropriate.”

“Smith believes in due process and has said so on the record numerous times,” Ms. Kasun said.

Other pastors have continued to associate with F.E.C. United. The week after its event at The Rock, the group held a meeting at Fervent Church in Colorado Springs. The event was emceed by the church’s pastor, Garrett Graupner.

Mr. Graupner also serves as F.E.C. United’s chaplain, a role he describes as simply ministering to the group’s members. “I’m the spiritual care guy,” he said. “If you asked me to be the chaplain of The New York Times, I’d say yes.”

Mr. Graupner has been an outspoken opponent of Covid restrictions throughout the pandemic, and he said his issues of greatest concern were not necessarily the election but rather abortion, gender identity and teaching about systemic racism in schools. “C.R.T.” — critical race theory — “is a hill for me to die on,” he said.

Nevertheless, he said, “I have seen some evidence to believe that the elections were tampered with at some point.”

“I could send you tons of material,” he said.