Image copyright Hannah Long-Higgins

Bernie Sanders is firmly the front-runner in the race to become the Democratic challenger to Republican President Donald Trump, fresh from a victory this week in the second state-by-state contest. His support is fervent but is his party, let alone the country, ready to embrace such an unusual candidate?

Bernie Sanders likes to call his presidential campaign a revolution, but these days it feels more like a touring rock concert.

The Vermont senator may seem like an unlikely front-man for bands like Vampire Weekend and The Strokes, but both have served as his warm-up acts, playing at recent campaign rallies.

But the thousands of fans in packed arenas reserve their loudest cheers for the scruffy-haired 78-year-old candidate with a clipped Brooklyn accent.

After nearly a year-long marathon of rallies, meetings, debates and ground-laying, the Sanders campaign is now entering a sprint of near-nonstop activity that will carry it through dozens of states across the country - an impressive test of endurance for a man who just months ago was hospitalised for a heart attack.

"Bernie Sanders is the only candidate that has given me the courage to believe that we cannot only demand bold, radical change, but that it's actually very attainable," said Aletha Shapiro, who travelled to New Hampshire from Long Island, New York, to help the Sanders campaign.

"If the people stick together, we can actually put power back in the hands of the people."

The end result of all this effort was a split decision in Iowa, as former South Bend, Indiana, Mayor Pete Buttigieg claimed the most delegates to the Democratic National Convention even though Sanders won a few thousand more votes.

In New Hampshire, Sanders finished narrowly ahead of Buttigieg again, with the two tied in the state's delegate count.

That didn't stop Sanders from claiming victory both in Iowa and New Hampshire on Tuesday night, however, and looking ahead to a showdown with Trump in November.

"The reason we won tonight in New Hampshire, we won last week in Iowa, is because of the hard work of so many volunteers," he said. "Let me say tonight that this victory here is the beginning of the end for Donald Trump."

The crowd, packed into a college gymnasium, responded with deafening applause, as though the volume of their cheers could will their beloved candidate to more victories in the days ahead.

Image copyright Hannah Long-Higgins

"It was electric," said Scott Sandvik, a music teacher from Boston. "I really think it was a release of tension after a nail-biter of an election."

If the Sanders "revolution" does take hold - an outsider campaign pitted as much against the Democratic Party's establishment as it is the incumbent president - New Hampshire could very well be seen as where it all began.

But the campaign still has a long road ahead.

Another shot at the prize

Four years ago, Sanders also followed a tight result in Iowa with a victory in New Hampshire. That contest was actually more decisive - a 20-point win over Hillary Clinton, who was considered the prohibitive favourite entering the race.

Sanders' 2016 New Hampshire triumph, however, was a springboard into an empty pool.

He followed his win in the overwhelmingly white New England state with a narrow loss in Nevada and a drubbing in South Carolina, where the Democratic voting population is majority black. Although there were a few bright spots after that - victories in Michigan and Wisconsin - Clinton spent the next few months pulling away from Sanders in the nomination race.

Image copyright Getty Images

Now Sanders is back, hoping history doesn't repeat itself. Facing a more crowded field, he appears to be in a much better position, as the nomination fight becomes a state-by-state slog on a battleground that stretches the breadth of the nation.

There is no Clinton machine waiting to do battle against the Sanders insurgency this time around. Instead, the Vermont senator heads out of New Hampshire along with a ragtag mix of candidates all scrambling for a foothold.

Joe Biden, the apparent front-runner through much of 2019, is grievously wounded by poor showings in the first two contests. Elizabeth Warren, the other candidate appealing to the liberal wing of the Democratic Party, has finished behind Sanders twice now and shows no signs gaining any ground.

Meanwhile, the continued presence of Buttigieg and Amy Klobuchar among the moderates of the party ensures middle-of-the road and establishment Democrats will remain divided.

Buttigieg has money, but a thin resume and doubts about his appeal to the more diverse rank-and-file of the Democratic Party. Klobuchar is counting on media coverage of her late surge in New Hampshire to make up for depleted campaign coffers and a virtually non-existent national organisation.

Who is Bernie Sanders?

Sanders had his first political victory in Burlington, Vermont, where he toppled the reigning six-term Democrat in 1981 for the mayoral seat by a margin of just 10 votes

Despite efforts by establishment Democrats to thwart his early career, Sanders served four terms as mayor before being elected to the US House of Representatives in 1990 - the first independent politician in four decades to do so

He won his current senate seat in 2007 and is currently in his third term

Sanders has an older brother, Larry, who lives in the UK and is currently the health and social care spokesman for the Green Party

The Sanders brothers: A tale of two underdogs

How Bernie Sanders always beat the odds

Image copyright Getty Images

Meanwhile, Sanders has risen in national polls as Biden has faltered. He boasts a veteran campaign structure that has basically been up and running since 2015, and a donor and volunteer network that spans the nation.

His $25m (£19m) fundraising haul in January alone will ensure he has more than enough resources to compete in every state on the crowded March primary calendar.

He has been officially or unofficially supported by figures from UK Labour MP Diane Abbott to YouTube star Joe Rogan. On Friday, he picked up another endorsement, from New York mayor and erstwhile 2020 candidate Bill de Blasio.

If Bernie Sanders isn't the Democratic front-runner at this point, the word has little meaning. He's far from a lock for the nomination, but his path ahead appears to be the clearest of any of his competitors.

On Tuesday night, Sanders essentially said as much.

"The reason I believe we are going to win is because we have an unprecedented grass-roots movement from coast to coast of millions of people," he said. "The reason that we are going to win is that we are putting together an unprecedented multi-generational, multi-racial movement."

Image copyright Hannah Long-Higgins

History is certainly on Sanders' side. Putting the Iowa popular-vote result in his column means the Vermont senator joins Al Gore in 2000 and John Kerry in 2004, both eventual nominees, as the only non-incumbents to win there and New Hampshire. In fact, no candidate has finished outside the top two in New Hampshire and gone on to the nomination.

"I think the people of the United States will unite around his message supporting the true hard working people of this country," said Tomas Amadeo of Hooksett, New Hampshire, echoing the optimism of many at the New Hampshire Sanders rally.

"He can resonate with people of all ages."

The current disposition of the Sanders campaign has his supporters hoping for the best, however, a big chunk of the Democratic establishment and moderates in the party are fearing the worst.

Incoming fire

Last Friday, in the spin room before the Democratic candidate debate in Manchester, senior Sanders campaign adviser Jeff Weaver was clear-eyed about what's in store for his candidate, as a Democratic establishment that views Sanders as a meddlesome and disruptive outsider prepares to fight back.

"There's always a target on his back," he said of Sanders. "They won't stop until they're beaten. Well, we're ready for it."

Image copyright Hannah Long-Higgins

In Iowa, Sanders was the subject of negative television advertisements from both the left and the right. The conservative Club for Growth aired a spot that painted the Vermont senator as an extremist - and said that his health was suspect after his heart attack last autumn.

A pro-Israel Democratic group ran an advert featuring Iowa voters saying Sanders couldn't beat Trump.

"It is no secret that our campaign is taking on the political establishment and the big-money interests who are now running negative ads against us in Iowa," Sanders said in response. "The billionaire class is getting nervous, and they should."

There's reason to believe Sanders' political-jujitsu strategy could be effective.

In 2016, as the Republican establishment finally acknowledged the threat that Donald Trump's candidacy posed, its scions - including 2012 Republican presidential nominee Mitt Romney - began to speak out. Their attacks only made Trump stronger, however, as he painted them as the "swamp's" last-gasp efforts to stop him.

"The establishment has never taken Sanders seriously, and now that they're having to they're going to attack him," said Caleb Gates, a Sanders supporter from Cedar Rapids, Iowa, who joined Sanders at a volunteer organisation event the day before the Iowa Caucuses.

"But I think that will only increase his appeal to a lot of people, especially those who are not politically active."

In New Hampshire, Biden and Buttigieg hit at Sanders directly, both warning he was too extreme to be the party's nominee and that his ideological views were too rigid.

Buttigieg accused Sanders of "dividing people with the politics that says, 'If you don't go all the way to the edge, it doesn't count', a politics that says, 'It's my way or the highway'."

What are his key campaign promises?

"Medicare for All" single-payer health system

Eliminate medical and student loan debt

Free public colleges, universities, trade schools

Green New Deal

Wealth tax

The wildcard

Time and again, it's the "electability" criticism that is used as a cudgel against Sanders, a self-described Democratic Socialist.

One recent poll indicated that more than half of Americans would not vote for a "socialist" president. Trump, at his rallies, regularly promises to his cheering support that "American will never be a socialist nation".

The "conventional" view of a Sanders candidacy can be summed up in in a tweet by Sean Trende, an elections analyst with the website RealClear Politics.

"Bernie Sanders is a complete wildcard," he wrote. "He could win by 10 points or lose by 20."

A blunter take by a Sanders critic was offered by New York Magazine's Jonathan Chait in a column that particularly irked the Sanders faithful.

"No party nomination, with the possible exception of Barry Goldwater in 1964, has put forth a presidential nominee with the level of downside risk exposure as a Sanders-led ticket would bring," he wrote. "To nominate Sanders would be insane."

When the stakes are so high - defeating Trump has been a central focus of Democrats since the day he was elected in 2016 - why, they ask, would the party choose a candidate so far away from the comfortable middle of American politics?

Image copyright Hannah Long-Higgins

Moderate members of Congress, in particular, have expressed apprehension about sharing a ticket with the independent-minded Vermont senator who only joined the Democratic Party to run for president.

Dean Phillips, a newly elected congressman from Minnesota who has endorsed Klobuchar, told CNN that Sanders could have a "disastrous" effect on congressional races in November, jeopardising the majority Democrats won in the 435-seat chamber in 2018..

"There are probably 25 to 30 seats that absolutely would be impacted directly by having a self-avowed socialist at the top of the ticket," he said. "He's not a Democrat, you know, and that's something that I wish was better understood."

Redefining 'electability'

The Sanders campaign clearly realises that winning the "electability" debate is essential to securing the party's 2020 nomination. It's why they hand out "Sanders beats Trump" stickers at their campaign events and chanted the refrain at his New Hampshire victory celebration.

They're quick to cite head-to-head polling that shows little significant difference between a Sanders-Trump matchup and one between Trump and Biden, the candidate frequently offered as the safe and electable option. A recent NBC/Wall Street Journal poll had Biden on top 50-44, while Sanders led Trump 49-45 - a statistically insignificant difference.

They also argue that the entire debate about electability is framed incorrectly. American politics, they say, isn't a battle for the middle, it's a battle of ideas and a battle for authenticity.

"What we did last time was nominate someone who was down the middle and another Washington person who wasn't going to change anything," said Pat Miguel Tomaino of Boston. "There are people hurting in this country who bought a lot of fake change from Donald Trump, and now we're all suffering for it."

Media playback is unsupported on your device Media caption ‘We voted for Obama, then Trump’

Tomaino, who volunteered for Sanders in New Hampshire, added that the economic collapse of 2008 destroyed the trust many Americans have in the current economic and political order, and unless the Democratic Party acknowledges this and adjust to the new reality, it's going to lose to Trump again.

"We have no illusion about elites coming to save us or tinkering around a little bit for a better technocratic way of ordering an elitist system where just 1% benefit," he said.

"We know that Bernie Sanders doesn't want any of that. We know he has our back, and we have his."

To pull this off, however, the Sanders campaign has to successfully identify and turn out voters who have sat out past elections. They're counting on the younger voters who polls show overwhelmingly back Sanders for the nomination, as well other disaffected Americans who have been marginalised by the system.

In Iowa, at least, the results were not encouraging. Although young voters made up a larger share of caucus participants, the total numbers were down from 2008, when Barack Obama's first campaign was electrifying many Democrats.

New Hampshire's numbers were better, but early indications are the higher turnout was in part due to moderate and independent voters showing up to support Klobuchar and Buttigieg.

Image copyright Hannah Long-Higgins

"I've always believed strongly that our case for winning this nomination and also beating Trump is that we can expand the base," said Faiz Shakir, the Sanders campaign manager.

"We have the most ambitious and difficult path to winning this nomination because it requires, by its nature, that people will be brought into this process."

He added that he thought the campaign had laid the groundwork for increased turnout in the states ahead, but there is reason the whole party should be concerned.

"We've got much more work to do," he said.

Take a closer look at the other candidates

New states, new troubles

As the focus turns to Nevada, which holds its caucus a week from Saturday, Sanders is facing criticism from a different direction. The state's powerful Culinary Union is circulating literature suggesting Sanders's plan for replacing private health insurance with a government-run programme will abolish their union-negotiated plans.

The union then released a statement saying that Sanders supporters, upon learning of the union's criticism, had "viciously" attacked the organisation.

Already Sanders' Democratic opponents, sensing a vulnerability in Nevada, are positioning themselves as defenders of union healthcare plans.

"Let's be clear: attacks on the union are unacceptable," Klobuchar wrote in a tweet. "I come from a family of proud union members and I know when unions are strong, America is strong"

Four years ago Nevada was the staging ground for Clinton's counterattack, as she won over union support in Las Vegas hotels and restaurants - even without an outright endorsement.

Media playback is unsupported on your device Media caption A family split over Bernie Sanders

If Sanders stumbles in Nevada again, the momentum he gained over the past two weeks could be lost, opening the door for one of the candidates he beat in New Hampshire - or for another, unexpected candidate who looms on the horizon in the weeks ahead.

Enter the billionaire

After Iowa and New Hampshire, the outcome of the race may be uncertain, but it has at least followed a somewhat predictable course. The field is narrowing as candidates struggle at the ballot box or run out of money. The hardiest campaigns have moved on to the later battlegrounds.

That may all head out of the window soon.

There hasn't been a presidential candidate quite like Michael Bloomberg.

The New York multi-billionaire is sitting out the first four Democratic nomination contests, and instead using his vast resources to campaign in later states, which award the lion's share of delegates to the Democratic national convention, where the party's standard-bearer will ultimately be decided.

The Bloomberg challenge presents one additional, unprecedented hurdle Sanders must clear if he wants to be the party's nominee - a circumstance not lost on the senator's team.

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"He's standing there waiting on Super Tuesday to try to block us if some if these other people can't," said Weaver of the Sanders campaign. "So, this race has got a long way to go and the ruling class in this country will do whatever it takes to stop Bernie Sanders."

Sanders's supporters have been even more blunt.

"It's not subtle at all what Michael Bloomberg is doing," says Tomas Armadeo of Hookset, New Hampshire. "It's very egregious how he's buying and funding his own way into this election. And I think people are going to see that."

Not everyone considers Bloomberg's presence as a threat, however.

"Bloomberg's a perfect foil for Bernie because Bernie has been railing against the billionaire class for decades," said Gates of Cedar Rapids. "And the chances of running against an actual billionaire, I think that plays right into his strengths."

That may be easy to say at this point, but if Bloomberg does become a serious obstacle for Sanders - and if he either denies the Vermont senator a majority of the delegates at the convention or becomes the nominee himself - there could be hell to pay from the Sanders faithful.

Image copyright Getty Images Image caption Former New York City mayor Michael Bloomberg has spent millions campaigning

Outside a Sanders canvassing rally in Newton, a tiny town in central Iowa, campaign volunteer Krissy Haglund hands out leaflets and says Bloomberg is a "test for the American people".

"I think it's a test to see if they're willing to believe that money should be out of politics."

Four years ago Haglund, a physician from Minneapolis, Minnesota, said the American people missed the "gift" that Sanders was offering them. And when presented with the choice between Clinton and Trump, she opted to vote for the Green Party's Jill Stein.

This time around, she's not sure she'd be able to support anyone but Sanders.

"I feel as though Bernie is in a class by himself and none of the other candidates are even close," she said. "And I think if he doesn't get it, it will be because of politics and not that he hasn't earned it in the numbers or from the American people."

And if it's Bloomberg, she's definitely looking elsewhere.

Follow Anthony on Twitter

Additional reporting by Haley Thomas

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