U.S. Senator Ted Cruz and retired neurosurgeon Ben Carson have made their Christian faith and the kind of issues that motivate faith-based voters a central part of their pitches to Iowa's heavily evangelical Republican caucus-goers.  

But in the state that will kick off voting for presidential nomination with its Feb. 1 caucuses, they're both being bested by Donald Trump, the thrice-married celebrity billionaire.

Cruz jumped out ahead of Trump in Iowa polls last month, largely on the strength of evangelical voters he poached from Carson. But with voting just days away, the New York businessman has surged back into a competitive position in Iowa.

Trump is now making overt moves to court evangelicals, most recently by making two high-profile appearances campuses known for their conservative brand of Christianity: Oral Roberts University in Tulsa, Oklahoma, and Liberty University in Lynchburg, Virginia.

On Friday, Trump's campaign cut a radio ad that will begin playing in Iowa and South Carolina, another evangelical stronghold and early-voting state, featuring a portion of a speech by Jerry Falwell Jr., the president of the Liberty University, delivered to introduce Trump.

Falwell is named after his father, the late Reverend Jerry Falwell, who founded Liberty University, along with the politically powerful "Moral Majority" in the 1980s. Falwell Jr. showered Trump with praise—though he stopped just short of an endorsement—while introducing the billionaire. 

"Donald Trump has stunned the political world by building an unlikely coalition that crosses all demographic boundaries of age, sex, race, religion and social classes and all party lines," Falwell said in the portion of the speech excerpted in the ad. "Donald Trump is a breath of fresh air."

Faith-based voters are traditionally an important component of the Iowa Republican caucus vote: In a Bloomberg Politics/Des Moines Register poll this month, 57 percent of likely Republican caucus-goers said they attend church at least once a week. In the December edition of the same poll, half of likely Republican caucus-goers identified themselves as "born again" or evangelical Christians.

Though Trump has begun to allude to his Presbyterian faith in speeches, he has not made religion a central part of his campaign in the same way some of his rivals have. 

Cruz and Carson have each made direct appeals to pastors within the evangelical community, with Carson frequently speaking at evangelical churches during Sunday services—events not advertised by his campaign staff. Cruz even launched an Iowa initiative in which he sought an endorsement from a pastor in each of Iowa's 99 counties, an evangelical version of a "Full Grassley." 

Cruz frequently ends his campaign rallies urging his supporters not only to vote—but to pray.

"Pray, lift up this country in prayer," Cruz told a crowd of a few hundred the day after the most recent debate at a rally in Columbia, South Carolina. "Spend one minute a day saying, 'Father God, please continue this awakening, this spirit of revival that is sweeping this country. Awaken the body of Christ that we might pull back from the abyss.'" He then recalled that former President Ronald Reagan was sworn into office with his hand resting "on Second Chronicles, 7:14."

Cruz, the son of a born-again Christian pastor, recited the passage verbatim from memory. And the stirred crowd nodded and murmured in approval.

Flash forward to earlier this week when Trump took to a podium at Liberty University. Students started an online meme poking fun at his attempt to quote "two Corinthians," more typically referred to as "Second Corinthians."

Trump's rough edges may be part of his appeal, said David Andersen, a political science professor at Iowa State University. 

"A lot of people come to Iowa and try to be evangelical. Voters can see through that. Donald Trump doesn't care about being anything but himself," he said. "Donald Trump is winning over evangelicals by being honest and not faking that he's evangelical."

Two other Republicans, Rick Santorum, a former U.S. senator from Pennsylvania, and former Arkansas Governor Mike Huckabee—who scored surprise wins in the 2012 and 2008 Republican Iowa caucuses, respectively, largely because of evangelical support—are also in the race again this year and seeking the same voters.

That crowded conversation has created an opening for Trump, Andersen said. "Evangelicals haven't coalesced behind any one candidate, and Trump has capitalized on this," he said.

Cruz and Carson, along with Huckabee and Santorum, frequently make their opposition to abortion and same-sex marriage key stump issues. Trump rarely, if ever, mentions abortion or gay marriage in his massive rallies, although he said that he is pro-life and supports traditional marriage in an interview with CNN this month.

Trump didn't mention either of the issues at his events at Liberty University and Oral Roberts University. And it may not have mattered much at the Oklahoma school, where Trump was introduced by former Alaska Governor Sarah Palin. 

The 2008 Republican vice presidential candidate and a conservative rock star whose latest book is a devotional, Palin praised Trump's power as representing the "fabric of of America [with it's] work ethic and dreams and drive and faith in the Almighty."

Before it's here, it's on the Bloomberg Terminal. LEARN MORE