On a clear, bright morning in Chicago, Marie Newman lists all the ways seven-term congressman Dan Lipinski has failed the city.
“This guy has been getting away with horrible, dangerous views and votes for 13 years,” she said in her campaign headquarters.
“He’s done absolutely nothing for working families. He’s on a mission against women for sure … He is anti-immigrant on every front.”
Such fierce attacks are not unusual between political opponents. The difference is both these candidates are from the same party: the Democrats.
Mrs Newman, a 53-year-old businesswoman, has entered politics for the first time not just to try and unseat Mr Lipinski, who represents Illinois’s 3rd congressional district in Washington, but also to send a message about the future of her party.
“He is a registered Democrat but he is not a Democrat,” she told the Telegraph. “I’m a real Democrat. I’m a true Democrat.”
Mrs Newman’s issues are ones shared by “progressives” across the country: $15 an hour minimum wage, Medicare – a government-funded health insurance – for all, better protections for illegal migrants and more gender equality.
Mr Lipinski, 51, backs some of that agenda, such as the $15 wage, but his team admit he is socially conservative. He opposes abortion on grounds of faith and voted against immigration reform, Obamacare and marriage equality.
He claims Mrs Newman lacks political experience and cautions against abandoning the centre ground. “Some people call for a Tea Party of the Left in the Democratic Party which I think is disastrous,” he said. “It is a terrible idea.”
The group is calling on left-wingers to “take the party back” by challenging moderate Democrats at the mid-terms, now just eight months away.
“What we wanted to do was to take the political revolution to Congress,” explains Waleed Shahid, the group’s 27-year-old communications director.
“The movement was never about Bernie himself, it was about the vision he campaigned on.”Mr Shahid has taken inspiration from Momentum, the Jeremy Corbyn activist group, and recently talked to the left-wing journalist Owen Jones for tips about mobilising voters.
Similar to Momentum, Justice Democrats rely on small donations for funding and have a support base of thousands ready to make calls and knock doors in targeted campaigns.
Mrs Newman is one of the 52 candidates the group has endorsed. “Unseating a Democratic incumbent is a special one for us,” says Mr Shahid. “We are very excited.”
The movement is causing ripples to surface right at the top of the US political landscape. Dianne Feinstein, a Democratic California senator for a quarter of a century, lost her local party’s support last month to a left-wing rival.
Democrat HQ has been accused of moving to block “radical” challengers to moderate candidates everywhere from Texas to Pennsylvania.
Even presidential hopefuls appear to have noticed the shift in the wind. Senators expected to seek the Democratic nomination – Elizabeth Warren, Kamala Harris, Cory Booker, Kirsten Gillibrand – all recently voted to keep the government shut down over the lack of a deal to protect illegal migrants, defying their party leadership.
For Mrs Newman, the decision to challenge Mr Lipinski for the safe Democratic seat was not a betrayal of the party – it was a defence of it.
She insists the race is “head-to-head” – though Mr Lipinski’s team claims their recent polling puts him in a double-digit lead. She plans to continue contacting voters from 5am until midnight until primary day on March 20, alongside the string of activist groups supporting her.
But whether she wins or loses, her message will have already been heard by the Democratic leadership: Change or face revolt.