Bernie Sanders has won the New Hampshire Democratic primary contest, on a terrible night for former vice-president Joe Biden.
The left-wing senator took a tight victory over centrist former mayor Pete Buttigieg, who offered a different Democratic vision in the race to take on President Trump in November.
Mr Sanders declared the night “the beginning of the end” of Mr Trump.
The race moves next to the Nevada caucuses on 22 February.
Finishing behind the Vermont senator were two moderates – Mr Buttigieg and Minnesota senator Amy Klobuchar, who emerged as a surprise contender by taking third place.
Massachusetts senator Elizabeth Warren and Mr Biden – two erstwhile frontrunners – finished in fourth and fifth places.
Technology entrepreneur Andrew Yang and Colorado senator Michael Bennet both dropped out of the race.
What happened in New Hampshire?
Some 280,000 Democratic voters cast ballots in the Granite State on Tuesday night, delivering 26% to Mr Sanders.
With 95% of the vote counted, Mr Sanders, 78, led Mr Buttigieg, the 38-year-old the former mayor of South Bend, Indiana, by only 1.6%, or about 4,300 votes.
Mr Sanders hailed a “great victory” as he thanked supporters from a rally in Manchester, New Hampshire.
“This victory here is the beginning of the end for Donald Trump,” he said, and promised to build an “unprecedented multi-generational, multi-racial political movement” to defeat the Republican.
The result will give Mr Sanders nine of the 24 delegates who will represent New Hampshire at the July Democratic national convention, where the party crowns a nominee based on the delegates won.
Although he had fewer votes, Mr Buttigieg will also get nine delegates. Thanking supporters, he warned against succumbing to “a polarised vision” of politics and pitched himself as the centrist to bring new voters into the party.
Pete Buttigieg finished a strong second, but his success outside the first two states is still an open question. Warren, his closest rival for the liberal left vote, has yet to prove she can finish near Sanders. Amy Klobuchar’s success ensures she’ll stick around and the moderate support will remain splintered.
In 2016 Sanders hit an electoral brick wall after New Hampshire. With plenty of money, a battle-tested national campaign organisation and divided opposition, his path ahead – while far from certain – looks the brightest of any in the field.
He would be the most left-wing candidate the party has nominated since George McGovern, however, and there are plenty of establishment Democrats old enough to have heart palpitations remembering the 1972 drubbing he took at the hands of Richard Nixon.
What had happened last week in the first contest?
The young former mayor led the delegate count going into New Hampshire after winning the Iowa caucuses.
Results there were delayed due to technical problems and the party, as well as several candidates, have demanded a re-tallying of the votes.
Unlike Iowa, New Hampshire’s contest is a traditional primary where voters cast secret ballots that are counted by the state, not the party.
Both states are largely rural and white, and not representative of the larger Democratic electorate.
A question remains over whether the frontrunners who have emerged from Iowa and New Hampshire can attract a broader coalition of voters that includes voters of colour.
Mr Sanders has polled as high as 19% among black voters, but in some polls, Mr Buttigieg has less than 10%. BBC