This week, the veteran senator pulled ahead of Hillary Clinton in Iowa – mirroring Jeremy Corbyn’s unlikely success in the UK. But a ‘democratic socialist’ couldn’t really beat the establishment frontunner, could he?

“Press 1 for revolution,” urge the hosts of a teleconference call for 17,000 union activists as they seek to sign up more volunteers for a leftwing insurgency.

Pundits scoff at their naivety, but opinion polls show the leader of this revolution – a grouchy socialist with unkempt white hair and a disdain for media niceties – pulling ahead of more-polished establishment rivals in the race to lead his party.

This grizzled veteran is proving a surprise hit on university campuses and social media, blending old-fashioned rallies with an online buzz that compensates for his lack of support from the party machinery.

Such a scenario might seem little more than a fantasy in an era of focus groups and political triangulation, but the remarkable fact is that this is the situation currently faced by parties on both sides of the Atlantic, in two countries with the most avowedly capitalist economies on the planet.

Bernie Sanders takes the lead over Hillary Clinton in Iowa poll Read more

The revolutionary hosting this particular conference call on Wednesday night was not Britain’s Jeremy Corbyn, but Bernie Sanders – his 74-year-old political doppelgänger from Vermont, who is seeking to become the Democratic party’s nominee for the US presidential election in 2016.

In many ways, Senator Sanders looks even more of a long shot than Corbyn. Though his politics are significantly less radical, he is seeking election in a country where what he describes as his “democratic socialism” is barely comprehended, let alone tolerated, by the political establishment.

His populist prescription might not raise that many eyebrows in Europe, with its calls for universal healthcare purchased by the state, publicly funded elections, free higher education, more protectionist trade policies and a redistributive tax system that raises money for job-creating infrastructure projects, but it represents a dramatic departure from the consensus in Washington. Furthermore, Sanders’ decision to eschew large campaign donations and rail against the power of Wall Street places him at a major disadvantage in a political system where successful presidential candidates are now expected to raise upwards of $1bn to stand a chance.

Like the 66-year-old Corbyn, his age, ethnicity and gender place Sanders at a disadvantage among progressives hungry for new faces in politics, something his focus on class and economic inequality cannot easily compensate for.

Facebook Twitter Pinterest Bernie Sanders (centre) after being elected mayor of Burlington, Vermont in 1981. Photograph: Special Collections, University of Vermont Libraries

Sanders is the longest-serving independent in Congress, representing Vermont in the Senate and House of Representatives since 1991. His non-conformist streak was apparent as mayor of Burlington in the 1980s, when he wrote letters to world leaders urging nuclear disarmament, and built on a reputation forged as a civil rights activist at the University of Chicago in the 1960s. While critics may dismiss him as a relic, it is this experience of the last great revolutionary period in American history that shapes his ambition, encouraging him to resist cosy compromises and seek to build a new counter-culture to support his quixotic bid for the presidency. To the shock of many Democrats, frontrunner Hillary Clinton has slipped behind him in polling conducted in the first two, influential states that will indicate their preference for the party nomination.

The last three polls in New Hampshire have all shown Sanders ahead – by an average of 7.6 percentage points – and his gradual whittling down of Clinton’s lead in Iowa appeared complete on Thursday, with the first survey showing him winning there too, albeit by a narrow one percentage point that was within the poll’s margin of error. Even more alarming for Democrat party officials, who still overwhelming favour Clinton, she has also lost her lead over potential Republican competitors in the general election – polling behind Jeb Bush and Ben Carson in the latest survey and drawing level with Donald Trump.

Many of Clinton’s troubles are homegrown. Her advisers admitted this week that they need to work on making her seem a more spontaneous candidate with more humour and heart on display. The former secretary of state also apologised for her decision keep professional emails hidden on a private computer server while she was in office.

But the positive surge in favour of Sanders has taken many by surprise, including the senator himself, who admitted he was “stunned” on Thursday.

This weekend, he continues a nationwide series of rallies that seem to have more in common with stadium-rock tours than the humdrum political encounters of many other candidates. An estimated 28,000 people turned up to see Sanders at a basketball arena in Portland, Oregon, in August. There were 15,000 at the Alaska Airlines Arena in Seattle, 11,000 at the Phoenix Convention centre in Arizona, 10,000 in Madison, Wisconsin and 8,000 in Dallas. For Sanders supporters, the upsurge of support is a sign of the hunger for radical political change among American voters.

“This is an incredible moment in history,” says RoseAnn DeMoro, director of National Nurses United, the first big labour union to endorse Sanders. “The self-organising is off the charts. It is hard for Bernie’s staff to keep up, but that is how political revolutions happen. This is what a revolution looks like,” she says.

The big question now is whether it can move beyond liberal bastions and predominantly white states such as Iowa and win over African-American and Hispanic Democrats, as well as some floating voters who might otherwise see themselves as Republican.

On Sunday, Sanders is due at the Greensboro Coliseum in North Carolina, and has so far attracted a more sedate 3,000 attendance confirmations on Facebook. On Monday he swings north with a rally at the civil war battle site of Manassas, outside Washington, and a speech at Liberty University in Virginia that could prove the most extraordinary moment yet in a campaign full of surprises. The evangelical Christian university was founded by televangelist Reverend Jerry Falwell, and is known for hosting only the most conservative Republican candidates on its campus. Texas firebrand Ted Cruz announced his candidacy for the party’s presidential nomination at Liberty, and its students and faculty are as far from natural supporters of liberal senators from Vermont as it is possible to imagine.

Facebook Twitter Pinterest Hillary Clinton polled an average of 7.6% behind Sanders in the latest polls from New Hampshire. Photograph: Louis Brems/AP

Whether Sanders is merely tolerated politely in the interests of academic pluralism or actually wins over any converts remains to be seen, but many believe there is a surprising overlap with supporters of Tea Party favourites such as Cruz, or the libertarian-leaning senator Rand Paul. They share Sanders’ deep distrust of the Washington establishment represented by both parties, which they believe has sold out to Wall Street and corporate interests.

Some of these disaffected Republicans, most notably those drawn to Trump, are also concerned at the hollowing out of US manufacturing and stagnation in middle-class incomes, which they blame on overly permissive trade policy and unfair competition from China. “There is a political rupture in this country,” says DeMoro. “Bernie is giving voice to a yearning that is out there, and that’s going to be very hard for the political establishment to overcome.”

“[Tea Party Republicans] see their life chances limited, their country deteriorating along with their hopes for their children,” she adds. “They identify government as the problem, but Bernie thinks the government is the problem too: government controlled by Wall Street and corrupted by corporate culture – he would agree with that.”

Arguably, this focus on the stagnant fortunes of middle-income Americans should not be seen as extremist at all. “Don’t let anybody tell you that we’re radical, that we’re outside the mainstream. We are the mainstream,” Sanders told Wednesday’s union conference call.

Proving this by reaching out to some disaffected Republicans would be nice, but a bigger and more pressing challenge for Sanders is to prove that he can appeal to the base of his own party. A major aim of this weekend’s campaigning in South Carolina and Georgia – where he will be joined by leading black academic Cornel West – is to try to prove to African-American voters in particular that his campaign’s focus on economic inequality is not incompatible with their struggle for racial equality. This tension has been thrust into relief by Sanders’ relatively muted response to police killings of young black men – something that has only recently become a feature of his speeches.

Sanders says he is sympathetic to some of the objectives of campaign groups such as Black Lives Matter, but seeks to place them in a wider context.

“When we have more people in jail than any other country on earth, we have a failed criminal justice system,” he told the Guardian in Iowa. “It means ending the militarisation of police departments, it means not having private corporations making money from the incarceration of Americans. It means having a radically different approach.”

So can Sanders reach beyond his white, liberal base?

“It’s not clear that he has more than a niche appeal,” says John Sides, a political scientist at George Washington University. “Democratic primaries are full of cases like this where someone will run at a more establishment candidate from the left.”Bill Bradley did it against Al Gore in 2000, and you could characterise Howard Dean’s candidacy that way in 2004 – but ultimately the polls prove to be a little like a sugar high, rather than a strong nourishing campaign.”

Jeremy Corbyn: like Bernie Sanders, UK politician is shaking up the mainstream Read more

Sides predicts the revolution could end with a backlash: “The thing that is going to hurt Sanders is that a lot of Democrats don’t think he is the best candidate to have at the top of the ticket. He’s quite well to the left. He’s a socialist. I mean, how many attack ads can you run on that little detail alone,” he says. “So you would see the party strike back in a big way. Even if he wins in Iowa and New Hampshire, it’s not going to convince the party that he’s a better candidate than Clinton, it’s just going to make the fight a little longer.”

Speaking on his way to the Sanders rallies in South Carolina, Cornel West disagrees. “We are now in an anti-establishment moment in this country, in both parties,” he says. “Brother Bernie Sanders has got authenticity, but also integrity: he has a long history of standing up for justice in the face of Wall Street and corporate power, and also standing up for black people. I can understand black brothers and sisters having a suspicion of politicians across the board. You can push for economic justice but you still have to deal with institutional racism, which is inseparable but not identical: it’s not simply a matter of economics, and I think Bernie Sanders understands that very well.”

“I think part of Bernie’s past is that he’s been up in Vermont for so long that he didn’t have a whole lot of black folk to direct it to. Now he recognises that he’s speaking on behalf of a national community all the time, he knows the issue of racism matters,” adds West, who plans to help the campaign communicate this, but believes it is already heading in the right direction.

“He’s already beginning to talk about how we deal with police brutality, voting rights and discrimination. The real challenge is making it integral to his basic speech so that anytime you talk about Wall Street domination, you always link in the issue of institutional racism. There is a real sense in which black folks can be the factor that puts him across the line. I really believe he can win. He’s not just on the move; he can win.”