Ted Cruz is projected to win the Iowa GOP caucuses based on an analysis of the vote so far, capping a furious race for the first-in-the-nation Hawkeye state.
Donald Trump was projected to finish second, Marco Rubio third and Ben Carson was projected to be in fourth place.
After Cruz was protected to win, Trump said he was honored about his finish.
"I'm really honored, and I want to congratulate Ted and I want to congratulate all the incredible candidates including Mike Huckabee who's become a really good friend of mine," he said. "So congratulations to everybody.
"We're leaving tonight and tomorrow afternoon we'll be in New Hampshire and that will be something special. It's going to be a great week."
Marco Rubio was ebullient as he addressed a raucous crowd of supporters.
“So this is the moment they said would never happen," he said. "For months they told us we had no chance ... because we didn't have the right endorsements or the right political connections, we had no chance. They told me that we have no chance because my hair wasn't gray enough and my boots were too high.”
Three-quarters of both Cruz’s and Rubio’s supporters were looking mainly for electability or a candidate who shares their values; by contrast, three-quarters of Trump supporters were mainly looking for someone who can bring needed change or who tells like it is.
The state Republican Party has said there was record-breaking turnout tonight.
A Republican source reports that there were a large number of "overflowing caucus sites," particularly in the central part of Iowa, closer to main population areas.
In polls conducted the past few days, Trump was in the lead. In a Des Moines Register-Bloomberg News poll released this weekend, Trump garnered the support of 28 percent of likely GOP voters with Cruz trailing by five percentage points.
In 2015, political outsiders Trump and Ben Carson led GOP polls in Iowa. In recent weeks, Cruz and Rubio gained some momentum.
With the New Hampshire primary eight days away, candidates will soon face another test of their viability.