Republican Ted Cruz and Democrat Hillary Clinton claimed early leads in the Iowa caucuses as voters begun meeting in schools, churches and other venues across the state.
Early results showed Cruz, the senator from Texas, holding a small but stable advantage over real estate mogul Donald Trump, The Washington Post reports.
Cruz was winning 28 percent of the vote to Trump's 25 percent, with 62 percent of the precincts reporting.
On the Democratic side, Clinton was leading 51 percent to Senator Bernie Sanders's 49 percent, with 69 percent of the precincts reporting.
Former Maryland governor Martin O'Malley had negligible support.
Voters gathered at caucus sites in 99 counties around the state. Political operatives predicted a high turnout and there were reports that some sites were so packed that officials had trouble closing the doors, despite a significant snowstorm that was bearing down on the state.
