WITH 99 per cent of the votes reported, US presidential hopeful Hillary Clinton led leftwinger Bernie Sanders by a nose in the Iowa Democratic caucus yesterday as Ted Cruz beat Republican rival Donald Trump.

Votes in several undeclared voting precincts were still being counted.

The Democratic race was so close in that tellers in six precincts were forced to toss coins to decide the result. Ms Clinton won them all.

State party chairman Andy McGuire said the result was “the closest in Iowa Democratic caucus history.”

With the Democratic caucus run on the basis of proportional representation, Iowa’s 44 delegates to the party’s national convention are likely to be split evenly between the two runners — former Maryland governor Martin O’Malley’s camp telling the media that he would suspend his campaign.

One-time clear favourite candidate Ms Clinton said she was she was “breathing a big sigh of relief.” But the result will be a wake-up call to her campaign.

“It is too late for Establishment politics and Establishment economics,” Mr Sanders said.

The socialist veteran is expected to romp home in next Tuesday’s New Hampshire primary, with polls giving him 55.5 per cent support to Ms Clinton’s 37.5.

Rightwinger Ted Cruz won the Republican contest with 26 per cent, beating populist buffoon Donald Trump’s 23 per cent.

“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 vowed to keep fighting, saying: “We will go on to easily beat Hillary or Bernie, or whoever the hell they throw up.”

Anti-Cuban mainstreamer Florida Senator Marco Rubio came a close third on 23 per cent. The only black candidate, creationist brain surgeon Ben Carson, came fourth with 10 per cent of the vote.

University of Birmingham academic Scott Lucas called Mr Rubio the real winner.

With recent polls placing the Floridan on 13 per cent, “no-one had expected the surge that almost took him into second place on Monday night,” Professor Lucas said.

But the surprise of the night was Jeb Bush’s relegation to sixth place with just 3 per cent of the vote, behind libertarian Rand Paul.