When Bernie Sanders was not battering Hillary Clinton at their latest debate for being a captive of Wall Street and falling short as a progressive, he was listing those things he would like to do as president, from free tuition for college students to free, guaranteed healthcare for all.

Then he had an admission. “For all these things to happen,” he said, “people have to rise up.”

This is the “political revolution” that is the rallying cry of Mr Sanders’ campaign for president and what he has been agitating for his entire political career, from before his election in 1981 as mayor of Vermont’s biggest city, Burlington, and his 25 years in Congress as an independent – he prefers democratic socialist – while aligning himself for voting purposes with the Democrats.

It is partly because of his reputation as an eccentric – a leftist dreamer – that Mr Sanders’ decision to run for president in 2016 was barely taken seriously at first. The Washington Post dismissed him as “an ex-hippie, septuagenarian socialist from the liberal reaches of Vermont who rails, in his thick Brooklyn accent, rumpled suit and frizzy pile of white hair, against the ‘billionaire class’.”

But suddenly, his moment – however big it turns out to be – is here. Polls predict a crushing victory in New Hampshire on Tuesday. He was barely pipped by Ms Clinton in the Iowa caucuses this week. Those who were there will not quickly forget Mr Sanders’ face when he greeted supporters in a Des Moines hotel ballroom after. He couldn’t speak for smiling and laughing.

Republican Ted Cruz compares himself to Bernie Sanders

If this was naked joy, who can blame him? Born in Brooklyn to Jewish parents – his mother from New York and his father from Poland – Mr Sanders’ road has been a long one. His first campaign was at his school when he ran for class president on a promise to start a fund for orphans of the Korean War. He lost. Once settled in Vermont, he ran four times as candidate for the anti-war, counter-culture Liberty Union party – twice for governor and twice for the US Senate – suffering solid defeats each time.

Finally, in 1981, he ran as an independent for Burlington mayor and won. He did what mayors are meant to do: get the snow-ploughs out on time and fill in the potholes. But already his idealism was driving him to go further. He decided, for instance, to turn Burlington into a beacon of opposition to the foreign policy of the Reagan administration.

In pictures: US Elections 2016 Show all 15 1 /15 In pictures: US Elections 2016 In pictures: US Elections 2016 Democratic U.S. presidential candidate Bernie Sanders speaks to supporters after rival candidate Hillary Clinton was projected as the winner in the Nevada Democratic caucuses Reuters In pictures: US Elections 2016 Democratic presidential candidate Hillary Clinton takes photos with workers at her campaign office in Des Moines, Iowa AP In pictures: US Elections 2016 Republican presidential candidate Mike Huckabee, second from left, prays before lunch with supporters at Drake Diner in Des Moines, Iowa Reuters In pictures: US Elections 2016 Democratic presidential candidate and former Maryland Governor. Martin O'Malley, speaks during a campaign stop in Waterloo, Iowa AP In pictures: US Elections 2016 Democratic presidential candidate Bernie Sanders speaks, as his wife Jane O’Meara Sanders looks on, at a campaign event at Iowa State University Getty In pictures: US Elections 2016 Republican presidential candidate Marco Rubio speaks at St. Ambrose University in Davenport, Iowa Reuters In pictures: US Elections 2016 Republican presidential candidate Ben Carson speaks at a campaign event at Fireside Pub and Steak House in Manchester, Iowa. Getty In pictures: US Elections 2016 Republican presidential candidate Rick Santorum visiting supporters at a house party in West Des Moines, Iowa Reuters In pictures: US Elections 2016 Republican presidential candidate Donald Trump at a campaign event in Cedar Rapids, Iowa AP In pictures: US Elections 2016 Republican candidate Ted Cruz campaigns at Greene County Community Centre in Jefferson, Iowa AP In pictures: US Elections 2016 Senator Rand Paul speaks during a Caucus rally at his Des Moines headquarters in Iowa Getty In pictures: US Elections 2016 Republican candidate Jeb Bush speaks at a campaign event in Des Moines, Iowa AFP In pictures: US Elections 2016 Former Alaska Governor Sarah Palin introducing the arrival of Donald Trump during a campaign rally in Cedar Rapids, Iowa Reuters In pictures: US Elections 2016 A portrait of Democratic candidate Bernie Sanders at his campaign headquarters in Des Moines, Iowa Getty In pictures: US Elections 2016 Campaign badges on sale ahead of a Trump rally at the Ramada Waterloo Hotel and Convention Centre in Waterloo, Iowa Getty

Burlington, population then about 30,000, having its own foreign policy seems as nutty now as it did to many then. Mayor Sanders, who had honeymooned with his first wife in the Soviet Union, travelled to Nicaragua to protest against American backing of the Contra rebels. He was greeted by the leader of the socialist Sandanista government, Daniel Ortega. It wasn’t long before his supporters in Vermont were being called “Sanderistas”. As mayor he also went to Cuba to visit President Fidel Castro.

There is nothing in the history books to suggest that Burlington did anything to alter the course of American foreign policy at the time. What the period does show, however, is a leader, albeit then of just a minor city, who rarely let the real world get in his way. Even before then he had been for gay marriage equality, long before the rest of America had even thought about it. His beliefs even as a student got him into trouble. He was arrested in Chicago for putting up leaflets protesting against school segregation.

Going against the grain in Congress has ensured his repeated re-election by Vermonters, first to the House of Representatives (1991-2007) and then the Senate. His approval rating in the state sticks at about 75 per cent. Over the years he has regularly separated himself from other Democrats: he opposed the welfare reforms introduced by former President Bill Clinton, has routinely decried the death penalty, voted against both the Iraq wars, and opposed the post-9/11 Patriot Act.

The Washington Post took Mr Sanders to task again this week. “Mr Sanders’s success so far does not show that the country is ready for a political revolution,” the paper opined. “It merely proves that many progressives like being told everything they want to hear.”

That, though, is the thing. A new Marist poll for the Wall Street Journal and NBC has Mr Sanders at 58 per cent versus Ms Clinton at 38 per cent in New Hampshire. Among men under 45 he is at 85 per cent. He is, more strikingly, 30 points ahead of Ms Clinton among women in the same age group. That “railing against the billionaire class” has touched a nerve, especially among younger voters who in Mrs Sanders’ long record see consistency and a sincerity they think Ms Clinton lacks.