Republicans and Democrats scrambling for their party's 2016 nomination for president descended on New Hampshire yesterday after Ted Cruz swept to victory over billionaire Donald Trump and Florida Senator Marco Rubio in the Iowa caucuses.
Among Democrats, Vermont Senator Bernie Sanders rode a wave of voter enthusiasm to a virtual tie with Hillary Clinton, long considered her party's front-runner.
The outcome in the country's first nominating contest drew a line under voter dissatisfaction, especially among Republicans, with the way government in Washington operates, with anger over growing income inequality and fears of global turmoil and terrorism.
Mr Cruz's victory in Monday's caucuses, which drew a record turnout, was a blow to businessman Mr Trump, who has roiled the Republican field for months with controversial statements about women and minorities.
Mr Cruz, a fiery, conservative Texas senator loathed by his own party's leaders, now heads to next Tuesday's first-in-the nation primary vote in New Hampshire as an undisputed favourite of the furthest right voters, including evangelical voters and others who prioritise an abrupt break with President Barack Obama's policies.
But Mr Trump still holds a commanding lead in New Hampshire and national polls.
"Iowa has sent notice that the Republican nominee and next president of the United States will not be chosen by the media, will not be chosen by the Washington establishment," Mr Cruz told supporters.
Mr Trump came in second, slightly ahead of Mr Rubio, whose stronger-than-expected finish could help cement his status as the favourite of mainstream Republican voters who worry that Mr Cruz and Mr Trump are too radical to win the November general election.
Mr Trump sounded humble in defeat, saying he was "honoured" by the support of Iowans. And he vowed to keep up his fight, telling cheering supporters that "we will go on to easily beat Hillary or Bernie or whoever the hell they throw up".
In the Democratic race, Iowa caucus-goers were choosing between Mrs Clinton's pledge to use her wealth of experience in government to bring about steady progress on party ideals and Mr Sanders's call for radical change in a system rigged against ordinary Americans. Young voters overwhelmingly backed Mr Sanders.
Mrs Clinton, the former secretary of state, US senator and first lady, was hoping to banish the possibility of dual losses in Iowa and in New Hampshire, where she trails Mr Sanders, who is from neighbouring Vermont. Two straight defeats could throw into question her ability to defeat the Republican nominee.
For Mrs Clinton's supporters, the tight race with Mr Sanders was sure to bring back painful memories of her loss to Mr Obama in the 2008 Iowa caucuses.
Mrs Clinton appeared before supporters to declare she was "breathing a big sigh of relief". She stopped short of claiming victory.
Mr Sanders had hoped to replicate Mr Obama's pathway to the presidency by using a victory in Iowa to catapult his passion and ideals of "democratic socialism" deep into the primaries.
"It is too late for establishment politics and establishment economics," Mr Sanders said.
He declared the Democratic contest in Iowa "a virtual tie".
Mr Sanders still faces an uphill battle against Mrs Clinton, who has deep ties throughout the party's establishment and a strong following among a more diverse electorate that plays a larger role in primary contests in February and March.
Iowa has long led off the state-by-state contests to choose delegates for the parties' national conventions. Historically, a victory has hardly assured the nomination, but a win or an unexpectedly strong showing can give a candidate momentum, while a poor showing can end a candidacy.
Some of the establishment Republican candidates have been focusing more on New Hampshire than Iowa, including former Florida governor Jeb Bush, Ohio governor John Kasich and New Jersey governor Chris Christie.
The caucuses marked the end of at least two candidates' White House hopes. Former Maryland governor Martin O'Malley ended his longshot bid for the Democratic nomination and former Arkansas governor Mike Huckabee dropped out of the Republican race.
The state's 30 Republican delegates to the national convention are awarded proportionally based on the vote, with at least eight delegates going to Mr Cruz, seven to Mr Trump and six to Mr Rubio.
Mrs Clinton led Mr Sanders 22 to 21, with the remaining delegate to be awarded to the statewide winner.
