Republican presidential candidate Marco Rubio greets a woman during a campaign event at the Sheraton Hotel in West Des Moines, Iowa on Tuesday. (Joshua Lott /for The Washington Post)

Marco Rubio’s first questioner was blunt: “On your decision-making, will you follow God’s word?”

For the next few minutes, Rubio sounded more like a Sunday school teacher than a presidential candidate holding an early January town hall. He talked about John the Baptist, he referred to Jesus as “God made man,” and he explained his yearning to share “eternity with my creator.”

Then, he answered the question: “Yes, I try every day in everything I do.”

As the Republican U.S. senator from Florida embarks on his final push before Monday’s Iowa caucuses, he is aggressively trying to persuade Christian conservative voters to support him. In TV ads, town halls and online videos, Rubio has been emphasizing his faith more than ever, wagering that showing his spiritual side will pay off in a state where 57 percent of GOP caucus-goers identified as evangelical or born-again Christians four years ago.

It is a challenging endeavor. Sen. Ted Cruz (Tex.), who sits well ahead of Rubio in recent polls, has established dominance on the Christian right, unifying an impressive roster of leaders and an army of churchgoing followers.

Donald Trump, who is running about even with Cruz in Iowa, won the endorsement of Liberty University President Jerry Falwell Jr. on Tuesday.

Some of Rubio’s opponents say the senator’s outreach has been too soft or that it simply has not worked. But Rubio, who lacks an obvious political base, senses an opportunity to win over some evangelicals to help himself at the margins.

He has signaled to top backers that he does not think he will win Iowa, setting his sights on a third-place finish that would give him a modest boost heading into New Hampshire.

“I do think it’s important for our president to be someone who is influenced by their faith, especially if it’s Christianity, because it is a faith that teaches you to care for the less fortunate, to seek peace, to care for one another, even to love your enemy,” Rubio told reporters Tuesday.

Speaking at a town hall before that, Rubio said the country should hope the next president is someone who “drops to their knees and asks the Lord for guidance.”

And a day earlier at a Des Moines rally where Sen. Joni Ernst (R-Iowa) introduced him, Rubio made a point of bringing up his faith without being asked about it.

“My wife Jeanette and I are raising four children right now, and we have to work harder than ever to ensure that our children grow up with the values they teach in our church instead of the values they are trying to ram down our throats in the popular culture,” he said, although his fondness for hip-hop music is well-documented.

Rubio’s religious background is unconventional. He is a practicing Roman Catholic, but he spent time as a member of the Church of Jesus Christ of Latter-day Saints when he was a child living in Las Vegas. He also attends a Southern Baptist megachurch with his wife.

Rubio is not generally seen by Republican voters as a culture warrior akin to Rick Santorum and Mike Huckabee, the past two winners of the Iowa Republican caucuses who are struggling this time around. But he impressed some pastors by declaring in the first GOP debate that he was opposed to abortion even in cases of rape or incest.

In a TV ad released Wednesday, Rubio says: “I believe in God.” In another recent ad, Rubio broadcast his antiabortion views and their religious roots. He also just formed a “Dignity of Life Advisory Board.”

“It’s not because I want to tell anybody what to do with their bodies or their lives, but because I believe that one of the fundamental rights given to us by our creator is the right to live,” Rubio says in the ad on abortion.

Nine days before that ad, he unveiled a commercial in Iowa called “Faith.”

“Our goal is eternity, the ability to live alongside our creator for all time. To accept the free gift of salvation offered to us by Jesus Christ,” he says in that spot.

Rubio’s campaign has also eagerly seized on a now widely viewed exchange he had with an atheist in Iowa who brought up concerns that he is running as “pastor in chief.”

He has raised money from it, sending out emails to supporters with the subject line: “I met an atheist.”

“No one’s going to force you to believe in God. But no one’s going to force me to stop talking about God,” Rubio responded. His campaign posted video of the exchange on YouTube.

Rubio’s most immediate goal, as recently communicated by his campaign to top backers, is to finish in Iowa and New Hampshire ahead of his party’s other mainstream candidates: former Florida governor Jeb Bush, New Jersey Gov. Chris Christie and Ohio Gov. John Kasich. None of them has made as explicit a push for Christian conservatives in Iowa as Rubio.

The Rubio team sees an overlap with Cruz in potential supporters. But Cruz is expected to do much better among Christian conservatives: He has the support of Bob Vander Plaats, a well-known Iowa Christian conservative activist, and is backed by prominent national figures such as radio host and Focus on the Family founder James Dobson.

Trump also has made surprising inroads in gaining evangelical support.

Some Christian conservative leaders, including Rubio’s own supporters, have complained that Rubio did not work hard enough to win the support of the movement.

Brad Cranston, a pastor from Burlington who is backing Cruz, said he does not see many evangelicals being drawn to Rubio. For many pastors, he said, Rubio represents “the establishment.”

Asked whether the candidate had reached out to evangelicals, Cranston said: “He’s attempted it. It hasn’t worked. There are just too many better options.”

Meanwhile, some Iowa ministers have questioned Rubio’s relationship with billionaire hedge-fund manager Paul Singer, a major benefactor who has fought to promote GOP candidates who support same-sex marriage. Rubio opposes gay marriage.

The heated competition for the support of Christian conservative voters in Iowa has made it difficult for some of them, such as Susan Lutz of Altoona, to confidently determine who speaks most directly to their values.

“We can’t discern that at this point,” she said after attending Rubio’s event in Des Moines on Monday.

Katie Zezima contributed to this report.