Hillary Clinton apparent winner of Iowa Democratic caucus: NBC News

In a night of surprises, Texas Sen. Ted Cruz rode a wave of strong evangelical support to a victory over national front-runner Donald Trump in the GOP's Iowa caucuses, according to NBC News. On the other side of the race, Democratic candidate Hillary Clinton appeared to have won the Iowa caucus after her rival, Vermont Sen. Bernie Sanders, dubbed it "a virtual tie."

"Based on the report from the Iowa Democratic Party Chair, we have marked Hillary Clinton as the apparent winner. The party described the race as a 'historically close caucus,'" NBC News said.

Much of the attention was on Trump, whose campaign rhetoric has focused on his ability to win — everything from business deals to the latest polls — so a loss in Iowa may blemish that image. In fact, Trump had led most recent statewide polls, and he even opted to skip the most recent debate. And he had spent weeks hammering Cruz with criticisms while campaigning in Iowa.

Sen. Ted Cruz.
Getty Images
Sen. Ted Cruz.

Recalling the doubts that "everybody" expressed about his chances in Iowa when he announced his candidacy, Trump said Monday night he was "honored" to come in second place, and he congratulated Cruz. Still, the businessman noted his first-place standing in New Hampshire polls for next Tuesday's primary, looking ahead to the next major test for his campaign.

Florida Sen. Marco Rubio delivered a triumphant address for his third-place finish, saying he will become the Republican nominee.

For his part, Cruz struck a populist tone in his victory speech.

"Iowa has sent notice that the Republican nominee and the next president of the United States will not be chosen by the media, will not be chosen by the Washington establishment, will not be chosen by the lobbyists, but will be chosen by the most incredible, powerful force — where all sovereignty resides in our nation — by we the people, the American people," Cruz declared.

Early entrance poll data had indicated a lead for former Secretary of State Clinton, according to NBC News. In that race, NBC News was allocating 30 of 52 delegates to Clinton, and 21 to Sanders as of 9:42 a.m. ET.

Clinton's campaign indicated to NBC News that it would be declaring victory in the state race, and the former first lady said she was "breathing a big sigh of relief" in her Monday night speech. In that address, Clinton characterized herself as a "progressive who gets things done for people," and as someone who stands in a "long line of American reformers who make up our minds that the status quo is not good enough."

The Republican National Committee, meanwhile, released a statement calling the Democratic Iowa caucus an "unmitigated disaster for Hillary Clinton and the Democrat Party," as the night's results were still too close to call between Sanders and her.

Sanders said just before midnight ET that the race appeared to be in a "virtual tie."

"When I think about what happened tonight, I think the people of Iowa have sent a very profound message to the political establishment, to the economic establishment and — by the way — to the media establishment," he said. "And that is that given the enormous crises facing our country, it is just too late for establishment politics and establishment economics."

Meanwhile, NBC News reported that former Maryland Gov. Martin O'Malley would suspend his campaign Monday night. And former Arkansas Gov. Mike Huckabee tweeted just before 10:30 p.m. ET that he had officially suspended his run for the GOP nomination.

Reports surfaced Monday evening that some precincts received many more caucus-goers than expected, with one county GOP leader telling NBC News that "we are busting at the seams." Entrance poll results from NBC News showed that 43 percent of Republican respondents said Monday's was their first caucus. For the Democrats, 59 percent said they were first-timers.

Monday's Iowa caucuses marked the first real report card for presidential hopefuls.

A win for a candidate does not by any means spell a nomination at his or her party's convention, but victory (or even a competitive placing) in Iowa can help build momentum into the rest of the year. On the other hand, a weak result in the state could mean the beginning of the end for some campaigns — especially in the crowded GOP field.

It remains to be seen how former Florida Gov. Jeb Bush, who spent the most money in Iowa but posted low numbers, will proceed now.

Of the 30 GOP delegates for Iowa, NBC News reported just before 1 a.m. ET on Tuesday that it was allocating eight for Cruz, seven each for Rubio and Trump, three for retired surgeon Ben Carson, and one each for Huckabee, Bush, Ohio Gov. John Kasich, Kentucky Sen. Rand Paul and former HP chief Carly Fiorina.

Trump has been the consistent GOP front-runner in major national polls, topping Cruz and Rubio — who were sitting in second and third place, respectively.

Within Iowa, all the recent pre-vote polls gave Trump a slight lead over Cruz in polls, but the Texas lawmaker had come in ahead of the real estate developer as recently as mid-January.

On the Democrat side, Clinton has led every major national poll, but Sanders has steadily gained ground since the summer.

In Iowa, Democratic expectations were mixed, with Sanders and Clinton locked in a virtual tie in most recent polls.

But there was a large bloc of undecided voters in both parties in Iowa and no certainty on who would turn up at the caucuses on a wintry evening, given that many supporters of Trump and Sanders are new to the process and disenchanted with traditional politics.

Iowa began both parties' nationwide nomination process, but its procedures are not well-known outside of the state. The state's Republican version sees caucus-goers attend meetings wherein they hear speeches from candidates' supporters, and then each person casts a secret vote.

For Democrats, the format is more public: Caucus-goers assemble in a room based on candidate preference, and if their favorite doesn't receive enough bodies to win a single delegate, then they can switch to another.

Iowa caucus winners have not necessarily fared well in their party's nomination process — especially on the GOP side. In 2012, former Pennsylvania Sen. Rick Santorum eked out a win over eventual nominee Mitt Romney, and Huckabee easily won the contest in 2008 — before eventually losing to Arizona Sen. John McCain.

Democrats, on the other hand, have seen their Iowa winner go on to win the nomination in each of the last three contested caucuses.

—Reuters contributed to this report.