Allentown, Pennsylvania, is the kind of place the national media brings up every now and then to talk about the troubles of the working class. That’s for good reason: the city is a great stand-in for America’s blue-collar blues. Billy Joel even wrote a song about it. The same goes for neighboring Bethlehem, which once was home to the largest steelmaking operation in the world. That operation shuttered in 2003 and was replaced by a casino.

No doubt the Lehigh valley has seen better days. But it’s not all in the rear view. In fact, this week this blue-collar bastion could decide the future of the Democratic party.

Pennsylvania’s seventh congressional district is among the most competitive in the country. In the last election only one percentage point separated Democrat Susan Wild (49.5%) and Republican Ryan Mackenzie (50.5%). Just over 4,000 votes made the difference. As a result, the Democratic party primary here has drawn national attention and the outcome has national implications: will Democrats embrace a blue-collar populism, or stick with the political insiders and liberal institutionalists that have failed the party in the past?

The candidates are instructive. First, there’s Lamont McClure Jr. McClure served two terms as the elected Northampton county executive. He’s a lawyer. His father was the executive director of the Carbon County Housing Authority. He’s quick to say that he’s the most qualified because “I’m the only one that’s ever been an elected official.” McClure has won a number of endorsements from local elected officials and Carbon county Democratic party insiders.

Then there’s Carol Obando-Derstine. Obando-Derstine worked as a top renewable-energy engineer; today she’s a non-profit executive. She served as US Senator Bob Casey’s senior Latino affairs adviser. She argues that her high-level experience in government and non-profit leadership make her right for the job.

Or consider Ryan Crosswell, another lawyer (and former registered Republican). Crosswell served in Barack Obama’s Department of Justice as a federal prosecutor. Before that, he worked with Littler Mendelson – a management-side labor firm that often represents companies responding to union organizing campaigns (Crosswell says he did not work on any union-busting campaigns). Today he’s running on an anti-corruption message: he believes “I have more expertise in anti-corruption laws … than anyone in Congress.”

These are the kinds of insiders that Democrats often elect – and they tend to lose in tough swing districts like these. In a sense the party is caught in a trap. As liberal voters have become wealthier and more educated, we’ve seen more and more candidates like these: lawyers, non-profit executives, senior advisers to so-and-so, professional policy advocates, holders of MBAs, etc. These professional-class progressives appeal to voters on the basis of their credentials, expertise and experience. While that works well among increasingly well-educated and well-heeled primary voters, it fails to win working-class voters in the much broader waters of a general election. Most voters just don’t identify with the credentialed elite. Many working-class voters actually resent them.

Only 33% of voters in Pennsylvania’s seventh district have a college education – 10 points lower than the national average. Some 38,000 work in manufacturing, about 27,000 work in warehousing and trucking and another 12,000 work in construction. Compare that with the roughly 14,000 professionals and you get a sense of how outnumbered the white-collar Brahmins really are.

Working-class voters simply prefer blue-collar candidates. They like electricians and schoolteachers more than attorneys and executives. That’s because working-class candidates better speak to the economic challenges most workers face, and they do so in plain language.

Luckily, there’s Bob Brooks. Brooks hasn’t had the privilege of a college education. He’s a veteran firefighter, and now head of the statewide firefighters union. His grandfather was a Teamster truck driver. He was raised by a single mother who worked as a bartender. He’s a varsity baseball coach at Nazareth high school. His campaign is unambiguously populist: “The Democratic Party has become the party of elites,” he has said. “Our politics are being bought and paid for, and we have to stop that”; “We’ve fought three wars since the minimum wage was last raised.”

Not surprisingly, given his labor record and union bonafides, he’s won the endorsement of a long list of local unions and area labor federations. What is surprising is that he’s also won the endorsement of the Pennsylvania governor, Josh Shapiro, and the US senator Bernie Sanders. He’s got the backing of Chris Deluzio, a congressman, in western Pennsylvania and Madeleine Dean, a congresswoman, of the Philadelphia suburbs. He’s got Elizabeth Warren and Ruben Gallego behind him. These are national party honchos, but more importantly, they are from totally different party factions. Brooks has managed to win the endorsement of the uber-progressive Working Families party and the famously moderate Blue Dog Pac. What is going on here?

One way to understand the intra-party tug-of-war is as a fight between progressives and moderates or liberals and centrists. But the biggest challenge facing the left today is not a straightforward policy question but instead a much larger social concern: how can progressives win back the working class? For those concerned with this question, populism has proven the obvious answer. Blue-collar outsider energy, a bold pro-worker program, a focus on jobs, wages, a “Made in USA” industrial policy, and an end to the disastrous era of free-trade and free-market lunacy that left only the very rich better off. That’s the combination that fueled ironworker Brian Poindexter’s primary victory in Ohio’s seventh district. It’s what’s powering the industrial mechanic Dan Osborn’s independent bid for the US Senate in Nebraska and the dark-horse candidacy of the ironworker Trey Martin in Oklahoma’s fifth congressional district.

Brooks fits the profile. He advocates for Medicare for All, repealing Citizens United, banning congressional stock trading, raising the minimum wage, new investments in infrastructure, labor law reform and free childcare. But, unlike down-the-line progressives, he also recognizes the need for a secure border, and for better resources for overburdened police and first responders. And unlike many elite liberals, Brooks talks about how he wants (and how the party needs) to win back blue-collar Maga voters, rather than sneer at them as “deplorables”. He blasts his own party for becoming out-of-touch and avoids the liberal penchant for culture warring. It doesn’t hurt that he drives a Chevy diesel work truck for his lawn care side gig (if anyone gets the pain at the pump, it’s Brooks).

He’s got what it takes to flip this district. Which is why the Republican party is already spending big money to influence the election. That’s frustrating, but it’s also a sign that Brooks is a real threat. Now it’s up to primary voters to see if Brooks has convinced them.

• Dustin Guastella is a research associate at the Center for Working Class Politics and the director of operations for Teamsters Local 623