In a windowless room next to a Salvation Army centre in rural Iowa, dozens of people are chanting: "We have nothing to lose but our chains! It is our duty to fight for our freedom! It is our duty to win!"
Mostly in their early 20s, they join hands in front of a sign saying, "The revolution will not be televised". Then they fan out across the state's cornfields, trying to convince Iowans that "democratic socialism" can save America.
These men and women are part of Bernie Sanders's volunteer army and it is unprecedented. They have arrived by plane, car and bus from across the US.
In January, they knocked at 500,000 Iowan homes. According to campaign data, they made seven million phone calls in the state. Through the 'Bern' app they have collected an ocean of granular data.
Mr Sanders (78) is no longer the surprise package he was in 2016, with his plans for Europe-style healthcare and free college fees. But his supporters grow ever more fervent.
Four years ago, he lost Iowa by a whisker to Hillary Clinton. His supporters are determined the revolution will not be quashed again.
"A lot of my friends supported Bernie in 2016 but didn't register to vote in time. No one's making that mistake again," said Michael Sayman (22), a volunteer from San Francisco. "My parents immigrated from South America, started a restaurant and lost it in the recession. We were evicted. It's because of that, the recession, that a lot of my generation have a different view of what should happen next in America. That's why we support Bernie."
For most of the week, Mr Sanders has been unable to join them. As a juror in Donald Trump's impeachment trial he cut an increasingly frustrated figure, fidgeting in his seat.
At the height of the trial he shuffled out of the Senate chamber for a call. On a stage 1,500km away in Iowa City, documentary maker Michael Moore, one of his celebrity campaigners, answered.
"Is that... Bernard from Brooklyn?" asked Moore. As Mr Sanders's voice crackled through a speaker, the crowd went temporarily insane.
"I'm sorry I can't be with you," Mr Sanders whispered, his voice heavy with cold. "But, as you know, we are impeaching the president." It was hard to hear him over screams.
Mr Sanders finally appeared, in front of 3,000 people, at a concert with rock band Vampire Weekend on Friday.
Rival Joe Biden visited 20 cities across Iowa in the final days, suffering awkward moments. After a climate change row, one voter accused the former vice-president of "pushing and poking" him.
Pete Buttigieg, the third-placed candidate, held up to five events a day. It takes only a short time to realise that Mr Buttigieg (38) is the smartest person in the room. He never misspeaks. No policy question throws him because he knows all the answers, and can probably deliver them in Norwegian if asked. His crowds do not go wild and are often more cerebral and moderate.
Regardless of who wins, and who becomes the Democrat nominee, they will have a hard time convincing Republicans in Iowa to vote for them in November. In 2016, Mr Trump beat Ms Clinton by 10 points.
On Thursday, the Democrat contest was overshadowed as Mr Trump arrived for a rally, far bigger than any Democrat has managed.
"I wouldn't vote for a single one of the Democrats," said Tonya Schwenn (49), an aluminium worker in a Trump hat. "They're way too overboard. The socialism aspect doesn't work for me. These Democrats are all a little bit scary, and Bernie's the scariest." (© Daily Telegraph, London)