Progressive US Senator Bernie Sanders has taken an early lead in New Hampshire's Democratic presidential primary, while former frontrunner Joe Biden trails badly.
Early on Monday afternoon (Australian time), Mr Biden was in fifth place in the second contest to find a nominee to face President Donald Trump in November.
With 14 per cent of precincts reporting in New Hampshire, Mr Sanders led with 28.4 per cent and Pete Buttigieg, the moderate former mayor of South Bend, Indiana, had 22.2 per cent.
Senator Amy Klobuchar, who was looking for a breakthrough after a strong debate performance on Friday, was in third with 20.5 per cent.
Mr Biden, the former US vice-president, was a distant fifth in the early results with 8.5 per cent, behind US Senator Elizabeth Warren with 9.4 per cent.
The Democrats seeking the right to challenge Mr Trump in the November 3 election have raced through the small New England state for a week, making their case for why they would be the best choice to beat Mr Trump.
Results began rolling in quickly after polls closed, and Democrats in New Hampshire were confident they would have smoother sailing than in Iowa, where embarrassing technical problems delayed vote-counting and the release of results for days.
Mr Buttigieg narrowly beat Mr Sanders in Iowa, but both campaigns have asked for a partial recanvass of the results.
Voters in New Hampshire chose a candidate from a ballot with 33 names, including some who dropped out weeks ago.
But it did not include former New York Mayor Michael Bloomberg, a billionaire who is not competing in any states before the 14 Super Tuesday primaries on March 3.
Mr Sanders had taken a lead in recent opinion polls in New Hampshire despite a barrage of criticism from rivals who warned his far-left views would lead the party to defeat against Mr Trump.
Mr Buttigieg also got a bump in polls after his narrow disputed win in Iowa.
Supporters of Mr Buttigieg greeted him at a Manchester polling place before dawn, waving blue and yellow "Pete 2020" campaign signs and chanting "President Pete".
Meanwhile, Mr Trump has easily won the Republicans' primary in New Hampshire, against minimal opposition.
Mr Trump was declared the winner as polls in the state closed on Tuesday night (local time).
Four years ago, the state offered Mr Trump his first primary victory and helped catapult him to the White House.