Story highlights
- The Iowa caucuses will serve as a test of whether Donald Trump can have lasting electoral success
- Polls indicated Trump ahead of Ted Cruz heading into caucus night
(CNN)Donald Trump's moment of truth is at hand as the Iowa caucuses are underway.
Everyone who was in line by 8 p.m. ET was allowed to take part in the caucuses -- the opening votes of the 2016 White House race, and the first test of the billionaire's ability to transform his media celebrity into electoral support.
And for Democrats, national front-runner Hillary Clinton is hoping to hold off upstart challenger Sen. Bernie Sanders and avoid a humiliating repeat of Iowa caucus night eight years ago, when she was felled by another improbable challenger -- Barack Obama.
Polls suggest that Trump, who has never run for any political office before, stands on the verge of a potentially stunning victory that would shake the Republican Party establishment. But Iowa caucuses are notoriously hard to predict and Texas Sen. Ted Cruz is banking on a strong turnout from evangelical voters to build a classic Iowa winning coalition.
Florida Sen. Marco Rubio, meanwhile, is hoping for a late surge that could defy expectations and offer him momentum heading into next week's New Hampshire primary.
Early returns around 9:10 p.m. ET found Cruz ahead in the Republican race 30% to Trump's 27% with 16% of the vote counted. Rubio was at 19%.
On the Democratic side, Clinton was ahead of Sanders 52% to 48% with 34% of the expected votes reporting.
Early entrance polls showed that two-thirds of voters in the Republican race said they were born again or evangelical Christians, higher than the equivalent share in 2012. Cruz had expected to run up support among the bloc, but the polls suggested its vote was being shared almost equally between the Texas senator, Trump and Rubio.
READ: The agony of Iowa's evangelicals
That's especially notable since all three candidates aggressively pursued the evangelical vote in the final days before the vote. Jerry Fallwell Jr., a prominent figure among conservative Christians, joined Trump on the campaign trail in Iowa over the weekend.
Visiting caucuses
Several candidates visited caucus sites on Monday evening. Trump mingled with voters at one West Des Moines location with his wife, Melania, and did some last minute campaigning.
"We are going to strengthen our borders, we are going to build a wall. We are going to bring our country back," Trump said, stirring cheers from some in the audience.
Long-shot candidate Carly Fiorina appeared at the back of the room at the same caucus site and waved to those inside. Cruz was also expected to head to a caucus location.
Several hundred thousand Iowans in 1,681 precincts are expected to venture out with scattered snow showers in the forecast to exercise their cherished right to cast the first votes in the race that will determine the 45th President of the United States.
The Iowa caucuses have huge symbolic power, and while they don't always predict who will be sworn in as the next president, they can offer a crucial boost to candidates who do well. They also spell doom for those who barely register and then do badly in the New Hampshire primary.
Earlier on Monday, Cruz, Trump's main GOP rival heading into tonight, said he's feeling "at peace" about the caucuses.
"I'm feeling good," he said on Glenn Beck's radio program. "I'm feeling at peace, and I'm feeling inspired."
If Trump emerges on top in Iowa, Cruz said he would "happily congratulate him."
READ: 5 things to watch in the Iowa caucuses
Even before the caucuses began, Carson's campaign said he wouldn't go directly to New Hampshire or South Carolina -- the site of the next primary contests. Instead, the retired neurosurgeon, who was briefly the Iowa front-runner last fall, will go to Florida to rest and see family.
Earlier on Monday, he told CNN's Wolf Blitzer insisted he could still post a strong finish.
"The people who support me are extremely enthusiastic," the retired pediatric neurosurgeon said.
Nervous night
Democrats are also bracing for a nervous night.
"So, ladies and gentlemen, I am officially running for president of the United States, and we are going to make our country great again," Trump told the crowd at his announcement.
"These are all of our stories," Cruz told the audience at Liberty University in Virginia. "These are who we are as Americans. And yet for so many Americans, the promise of America seems more and more distant."
"Grounded by the lessons of our history, but inspired by the promise of our future, I announce my candidacy for President of the United States of America," Rubio told supporters at Miami's Freedom Tower.
"Yes, I am running," Fiorina said on ABC's "Good Morning America." "I think I'm the best person for the job because I understand how the economy actually works. I understand the world; who's in it."
"I'm probably never going to be politically correct, because I'm not a politician," he said in his announcement. "I don't want to be a politician. Because politicians do what is politically expedient -- I want to do what's right."
"Today I announce with God's help, with the help of liberty lovers everywhere, that I'm putting myself forward as a candidate for President of the United States of America," Paul said at the rally.
"We will get back on the right side of free enterprise and freedom for all Americans," Bush said during his announcement.
"I am here to ask you for your prayers, for your support ... because I have decided to run for president of the United States," Kasich told his kickoff rally at the Ohio State University.
"I truly am from Hope to higher ground," Huckabee told the crowd during his announcement. "So it seems perfectly fitting that it would be here that I announce that I am a candidate for President of the United States of America."
"As middle America is hollowing out, we can't sit idly by as big government politicians make it harder for our workers and then turn around and blame them for losing jobs overseas. American families don't need another President tied to big government or big money," he said during his kickoff rally.
"We need a government in Washington D.C. that remembers you went there to work for us, not the other way around," he said during the rally.
"Everyday Americans need a champion, and I want to be that champion -- so you can do more than just get by -- you can get ahead. And stay ahead," she said in her announcement video. "Because when families are strong, America is strong. So I'm hitting the road to earn your vote, because it's your time. And I hope you'll join me on this journey."
"This great nation and its government belong to all of the people and not to a handful of billionaires, their super PACs and their lobbyists," Sanders said at a rally in Vermont on May 26.
"This is the urgent work calling us forward today: to rebuild the truth of the American Dream for all Americans," O'Malley said at his rally. "And to begin right now."
Clinton expressed confidence about her prospects earlier Monday and reiterated her argument that Sanders won't be able to deliver on some of his ambitions policy proposals.
"I am a progressive who wants to make progress and actually produce real results in people's lives. That's what I'm offering," she said on CNN's "New Day." "I'm not overpromising."
The former secretary of state, and her husband, former President Bill Clinton, eased their nerves ahead of the caucuses with a walk around Gray's Lake in Des Moines, leaving staffers behind.
READ: The Iowa caucuses, explained
On the eve of the caucuses, the race to win Iowa turned more sharply combative as candidates desperate for an edge dashed through a frenzied final day of campaigning.
Trump branded Cruz a "liar" and made a play for the Texas senator's evangelical power base. Cruz questioned Trump's conservative authenticity on abortion and religious liberty and appeared alongside Duck Dynasty's Phil Robertson, who branded same-sex marriage "wicked" and "evil."
Sanders complained that he could not keep up with distortions of his record made by the Clinton camp. And a former aide to President Barack Obama took to Twitter to accuse the Vermont senator of repudiating their old boss' record.
Clinton is positioning herself as the most qualified commander in chief and the best person to save Obama's legacy. But Sanders is vowing to stage a "revolution" that will overturn a corrupt political structure bankrolled by a busted campaign finance system that he says is soft on Wall Street and favors the wealthy.
A win for Clinton would give her leeway to weather what could be a loss in New Hampshire next week and allow her to pivot to South Carolina, where minority voters could provide a firewall against a Sanders surge.
Cruz under pressure
Cruz is under intense pressure to deliver a victory on Monday night since Iowa is a state perhaps most receptive to his appeal to the most ideological conservatives and evangelicals. A defeat would cast doubt on his wider appeal in the delegate-rich Southern states he hopes could pave the way to the nomination.
Cruz is also drawing fire from his other flank, as Rubio seeks at least a third-place finish to make the case that he is a stronger alternative to Cruz and Trump than ex-Florida Gov. Jeb Bush, New Jersey Gov. Chris Christie and Ohio Gov. John Kasich.
"This whole notion Ted has that he's the only conservative, I think as people learn more about his record, they'll realize what he really (is) is very calculating," Rubio told CNN's "State of the Union" on Sunday.