CLINTON SIGHS, SANDERS SMILES

The results of the Democratic race put pressure on Clinton to siphon support away from Sanders, who has won over politically left-leaning voters with his promises to take on Wall Street and start fresh with healthcare reform.

Clinton, 68, said she was breathing a "big sigh of relief" after the results. She lost Iowa to then-Senator Barack Obama in the 2008 Democratic race and never recovered.

The former first lady congratulated Sanders and did not declare victory in her remarks. Her spokesman Brian Fallon, however, said numbers showed she would emerge with two more delegates from Iowa than Sanders, a victory. Delegates determine the party's nominee at a convention in July.

"It is rare that we have the opportunity we do now to have a real contest of ideas," Clinton said with her husband, former President Bill Clinton, and daughter Chelsea joining her on stage.

U.S. Democratic presidential candidate Bernie Sanders poses for a selfie with a supporter during his caucus night rally in Des Moines, Iowa February 1, 2016. [Photo/Agencies]

Sanders, 74, declared himself overwhelmed. The lawmaker, who smiled broadly as he addressed supporters, is leading in New Hampshire, home to next week's second contest, but trails Clinton in other states such as South Carolina, which holds the third contest.

"Nine months ago, we came to this beautiful state, we had no political organization, we had no money, we had no name recognition, and we were taking on the most powerful political organization in the United States of America," Sanders said.

Former Maryland Governor Martin O'Malley, who had trouble gaining any traction in the Democratic race, suspended his campaign after coming in third in Iowa with 0.6 percent.

The 2016 election is shaping up to be the year of angry voters as disgruntled Americans worry about issues such as immigration, terrorism, income inequality and healthcare, fueling the campaigns of Trump, Sanders and Cruz.

Republican establishment candidates more traditional than Rubio did not fare well in Iowa. Former Florida Governor Jeb Bush took 2.8 percent, Ohio Governor John Kasich took 1.9 percent, and New Jersey Governor Chris Christie took 1.8 percent.

Surgeon Ben Carson placed fourth among Republicans with 9 percent while former Arkansas Governor Mike Huckabee said he was suspending his campaign for the party's nomination. Huckabee won the Iowa caucus in 2008.

Market reaction in Asia to the results was muted, with U.S. stock futures down around half a percent.

"Financial markets might be more comfortable with Hillary (Clinton) than Bernie (Sanders)," said Sean Callow, a strategist at Westpac Bank in Australia.

"There would have to be at least some jitters over the guy who plans to break up the big banks. But it's probably too early to expect the U.S. presidential race to have an impact on the U.S. stock market."