Joe Raedle/Getty Images Ted Cruz is counting on Iowa's evangelical voters to lift him to victory in the caucuses.

CLIVE, Iowa -- Ted Cruz is a U.S. senator from Texas, but by the end of his speech here Wednesday night, he sounded more like an evangelical preacher urgently gathering the flock.

Touted by his introducers as a "man of Christ," Cruz lowered his head in reverence to God and Iowa caucus-goers.

"I ask you to pray," he told the crowd of about 600 at a meeting hall in Clive, a Des Moines suburb. "I want you to lift this country up in your prayers to power this revival, to create this community in the body of Christ."

His campaign was based, Cruz said, on a passage from the Bible -- 2 Chronicles 7:14 of the Old Testament -- in which God promises to protect the Israelites if they accept him.

"If my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways," Cruz recited, "then I will hear from heaven and I will forgive their sin and will heal their land."

The message: God will heal America -- but only if you vote for Ted Cruz next Monday.

There was urgency in Cruz's voice for a very good reason, and his name is Donald Trump.

Evangelical Christians, who usually represent about half of the voters in the Republican presidential caucus in Iowa, were supposed to be Cruz's springboard to the White House. The son of a well-known preacher, the 45-year-old Cruz has tailored his career to appeal to such voters. Intellectually brilliant and superbly educated, Cruz presents himself as a shrewd lawyer who can use sacred texts -- the Bible and the U.S. Constitution -- to force the courts and Congress to make America a conservative utopia.

But then along came Trump, with his nakedly racist, anti-Muslim and xenophobic appeals; his own secular version of the Apocalypse (immigration and the Islamic State); and his own version of the savior who can solve all problems -- himself.

Chip Somodevilla/Getty Images Donald Trump is building up evangelical support -- at least in polls.

Theologically, evangelicals are Protestants who say they have, and have chosen, a direct personal relationship with Christ; who believe the words of the Bible are literal and infallible; and who feel an individual duty to "spread the word" of God to others.

Speaking to evangelicals, Cruz is most comfortable pushing social issues (against abortion and same-sex marriage, in favor of public displays of faith) and antagonism to "big government." But Trump has made surprising inroads by raising fears about undocumented Mexicans here and terrorists everywhere, and by calling for an economic nationalism in which "big government" can be a weapon.

As a result, Trump -- who until recently was pro-choice on abortion and tolerant on matters such as gay marriage -- is actually leading Cruz among evangelicals nationwide. More to the immediate point, he is surprisingly competitive with Cruz among evangelicals in Iowa. Cruz was backed by 39 percent in a recent poll, but Trump garnered 27 percent.

After earlier efforts to avoid clashes, Cruz is now attacking Trump furiously on the campaign trail and in TV ads. The main points: Trump has flip-flopped on abortion and is a New Yorker who offers only a phony conservatism on "faith issues."

Cruz assembled a choir of anti-abortion leaders to make that case at the town hall meeting in Clive.

Julie Muselman, from the nearby town of Waukee, loved what she heard. She fears Trump as a false messiah and she praised Cruz.

"He is honest, truthful and smart," said Muselman, 62. "And I think he is also a committed Christian, which means he has taken Christ into his heart."

Muselman is an evangelical Christian who first got involved in Iowa presidential politics in 1976, when she voted in the Democratic caucus for Jimmy Carter, the first national candidate to appeal directly to evangelicals in biblical language. Now a Republican, she has voted for GOP candidates who ended up winning the caucuses: then-Arkansas Gov. Mike Huckabee in 2008, then-Sen. Rick Santorum of Pennsylvania in 2012.

Neither of those last two men went on to win the nomination, which is often the case with the GOP winner of the Iowa caucuses. But in the process of competing in Iowa, Republican candidates pull themselves -- and their party -- further to the right as they alter their stands to suit the state's religious voters.

Trump has been racing to the right at top speed. He has sought and won the endorsement of key religious conservatives such as Jerry Falwell Jr. -- who leads Liberty University, an influential evangelical institution founded by Falwell's father, himself a key supporter of Ronald Reagan in 1980.

I think he is also a committed Christian, which means he has taken Christ into his heart. Iowa resident Julie Muselman praising Ted Cruz

If Cruz doesn't draw a huge turnout among evangelicals, he and his aides concede, they are likely to lose the caucuses.

On Sunday, just one day before caucus-goers gather, pastors in evangelical churches across the state will be speaking on this question -- Trump vs. Cruz -- even if they don't necessarily mention the two by name.

Attacks and appeals based on faith (or lack thereof) have been common in U.S. politics almost since the beginning. The Republican Party of today is something new: a European-style religious party powered (and trapped) by the cultural traditionalism of evangelical Protestants and conservative Catholics.

That gives Iowa outsized influence, because early in the primary season, Iowa Republicans put all the candidates on record as believers in the right-wing Gospel. And it makes the Iowa caucuses a test of the power of evangelicals. A Trump victory would be seen as a loss not just for Cruz.

But Cruz is going to need help -- and perhaps some divine intervention -- to win.