Just months after a heart attack seemed to signal an all but certain end to his presidential aspirations, Bernie Sanders has established himself as the narrow-but-clear frontrunner for the Democratic presidential nomination with a slim primary win in the New Hampshire primaries.

It's a win that comes four years after Granite State voters took it upon themselves to buck the Democratic Party establishment’s choice of candidate in his favour, launching an improbable political arc his supporters now see as a political movement with its best chance at reaching maturity.

Unlike that 2016 win, though, Tuesday’s win over second place Pete Buttigieg in New Hampshire marks a leader ascendant, instead of a surprising and novel political force. And perhaps above all, the results signal the start of what will undoubtedly be a fierce battle between the democratic socialist and that same entrenched party establishment, and its fundraising tradition he has not been shy to criticise.

“This is a movement from coast to coast that is demanding that we have an economy and a government that works for all of us,” Mr Sanders during a victory speech in Manchester.

“We are taking on billionaires and we’re taking on candidates funded by billionaires,” he continued, in a veiled shot at Mr Buttigieg, who has hit criticism in this race for his courting of high dollar donors, including a fundraiser in a California wine cave.

Democratic candidates compete on the campaign trail: In pictures Show all 18 1 /18 Democratic candidates compete on the campaign trail: In pictures Democratic candidates compete on the campaign trail: In pictures Jessica Canicosa, a precinct captain for Bernie Sanders, waits to greet caucus voters at Liberty High School in Henderson, Nevada REUTERS Democratic candidates compete on the campaign trail: In pictures Hotel workers at the Bellagio in Las Vegas get to grips with voting papers during the Nevada caucuses AFP via Getty Images Democratic candidates compete on the campaign trail: In pictures A caricature of Bernie Sanders is projected on to a tree during a rally in Las Vegas EPA Democratic candidates compete on the campaign trail: In pictures A woman waits to have a photo taken with Elizabeth Warren during a town hall meeting in Las Vegas REUTERS Democratic candidates compete on the campaign trail: In pictures The threat of coronavirus and other germ-borne illnesses was on some voters' minds at the Democratic caucuses in Henderson, Nevada Getty Images Democratic candidates compete on the campaign trail: In pictures Former vice-president Joe Biden takes a selfie with a voter in Las Vegas ahead of the Nevada caucuses REUTERS Democratic candidates compete on the campaign trail: In pictures Amy Klobuchar changes her shoes backstage after giving a speech in Exeter, New Hampshire AFP/Getty Democratic candidates compete on the campaign trail: In pictures A warmly-wrapped-up dog attends an Elizabeth Warren event at Amherst Elementary School in Nashua, New Hampshire AFP/Getty Democratic candidates compete on the campaign trail: In pictures Bernie Sanders, who romped to victory in New Hampshire against Hillary Clinton in 2016, talks to the media in Manchester Getty Democratic candidates compete on the campaign trail: In pictures Joe Biden was hoping to improve on his poor showing in Iowa in the New Hampshire primary Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren, renowned for giving time to supporters for selfies, works the crowd at the University of New Hampshire in Durham Getty Democratic candidates compete on the campaign trail: In pictures Joe Biden takes a selfie with a supporter and his child outside a campaign event in Somersworth, New Hampshire on 5 February Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren and Bernie Sanders quarrel after a confrontation in a TV debate in which Sanders claimed that Warren was not telling the truth about a conversation in which she claimed he had said a woman could not win the presidency on 14 January AP Democratic candidates compete on the campaign trail: In pictures Supporter Pat Provencher listens to Pete Buttigieg in Laconia, New Hampshire on 4 February Getty Democratic candidates compete on the campaign trail: In pictures Pete Buttigieg speaks at a campaign event in Concord, New Hampshire while awaiting the results of the Iowa caucus Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren is presented with a balloon effigy of herself at a campaign event in Nashua, New Hampshire on 5 February Reuters Democratic candidates compete on the campaign trail: In pictures A Trump supporter rides past a rally for Amy Klobuchar in Des Moines, Iowa on 14 January AP Democratic candidates compete on the campaign trail: In pictures A man holds up a sign criticising billionaires in the presidential race in front of Michael Bloomberg in Compton, Califronia. The former New York mayor skipped the first caucus in Iowa and instead campaigned in California on 3 February Reuters

Mr Buttigieg, speaking from Nashua just before the Vermont senator took the stage across the state, revelled in his second strong performance, and promised to keep moving forward.

“Here in a state that goes by the motto, ‘Live Free or Die,’ you made up your own minds,” Mr Buttigieg said to applause. “You asserted that famous independent streak. And thanks to you, a campaign that some said shouldn’t be here at all has shown that we are here to stay.”

In the Southern New Hampshire University gym where Mr Sanders held his election night party, a silent feed of CNN’s election coverage played above press risers throughout the night leading up to his victory speech.

The vibe was decidedly anti-Buttigieg, and expressed a raw desire for massive change to America’s economic and political status quo.

As results poured in showing Mr Sanders in top of the field, those supporters periodically erupted in cheers and chants of “Bernie! Bernie! Bernie!” with each major development in the numbers — and the enthusiasm continued even as it became clear that the results would not give Sanders the kind of blowout victory he had against Hillary Clinton in 2016.

When Mr Buttigieg took the stage just a half hours drive south in Nashua, the crowd booed the former mayor of South Bend, before starting a “Bernie beats Trump” chant as the 38-year-old beamed on screen.

“Wall Street Pete!” they continued to chant during that speech.

AOC whips up the crowd at Bernie Sanders campaign event

Amy Klobuchar, who has been running a campaign that flew largely under the radar of the national media, suddenly found her stock rising with her third place win. At her Nashua election night party, she celebrated the showing, and her newfound status as this year’s New Hampshire surprise.

“Hello, America. I’m Amy Klobuchar and I will beat Donald Trump,” she said. “My heart is full tonight. While there are still ballots left to count, we have beaten the odds every step of the way.”

The results in New Hampshire almost instantly narrowed the once burgeoning field of presidential candidates, with Andrew Yang and Michael Bennet reading the tea leaves early and suspending their campaigns long before Sanders went on stage to declare victory.

“I am the math guy and it is clear to me from these numbers we are not going to win this race,” Mr Yang told supporters.

But two prominent candidates who drew disappointing results on Tuesday in New Hampshire, Elizabeth Warren and Joe Biden, remained defiant, and pledged to soldier on into what could become a protracted and ugly fight that extends into convention this summer.

In a speech to supporters at a tennis hall just across the road from the Manchester airport, Warren thanked her dog Bailey for his support and praised Ms Klobuchar’s third place showing, warning the world to never underestimate a woman with determination.

“I also want to congratulate my friend Amy Klobuchar for showing just how wrong the pundits can be when they count a woman out,” Ms Warren said.

Then, she expressed her own determination to stay in the fight after less than stellar results in Iowa and now New Hampshire.

“I also want us to be honest with ourselves as Democrats: we might be headed for another one of those long primary fights that lasts for months, she said before warning of the dangers of factionalism that may result from the attacks that have sprouted up among Democrats this past week.

“We’re two states in, with 55 states and territories to go. We still have 98 per cent of the delegates for our nomination up for grabs, and Americans in every part of our country are going to make their voices heard.”

Joe Biden, who has left the state before polls even closed, addressed his supporters from South Carolina, where he is banking on strong African American support to breathe life into his cratering campaign.

“I do love New Hampshire, I really mean it,” he told his supporters via telecom during an address in which he appeared at one point confused, mixing up the names of Nevada and New Hampshire.

“It ain’t over, man, we’re just getting started,” he said.

But Democratic voters were not the only ones to cast votes on Tuesday. Donald Trump— who voters in the state almost universally said was their top issue, meaning they want him out above all else — was also on the ballot, which he won again with very little resistance.

And, apparently watching results come in alongside everyone else, the president lashed out, showing just the kinds of attacks in store for Democrats I’m the general election.

“A lot of Democrat dropouts tonight, very low political IQ,” he wrote in one tweet among many that included an attack on Mr Sanders over how close Mr Buttigieg had come to winning — “very interesting!” — and one on Ms Warren that used a racially charged attack as he slammed her poor performance.

Mr Sanders was looking ahead too.