BEATRICE, Neb. — In the back room of a brewery in southeastern Nebraska, more than three dozen people crowded together this summer to hear from Dan Osborn, a former cereal plant worker and independent running for U.S. Senate.

The standing-room-only crowd in the small town of Beatrice was larger than Osborn expected, but it stood out for more than its size. Those attending ranged from supporters of former President Donald Trump wearing “Make America Great Again” hats to voters firmly backing Vice President Kamala Harris and other Democrats.

Osborn’s message to all of them was that America’s two-party system has let them down.

“There’s nobody like me in the United States Senate,” he told the crowd. “Right now, the Senate is a country club of millionaires that work for billionaires.”

Osborn has cobbled together a campaign in deeply conservative Nebraska that rejects both major political parties as part of a broken system. For a guy who held his first campaign news conferences out of the garage of his suburban Omaha home, he has surprised pundits by emerging as a serious challenger to two-term Republican Sen. Deb Fischer in what had been considered a safe Republican seat only months ago.

The contest has attracted $21 million in spending from outside groups, favoring Osborn, and even Fischer’s campaign acknowledges that the race is closer than expected. There is no Democratic candidate running, but a win for Osborn could disrupt Republican plans to reclaim a majority in the Senate. Osborn has said he won’t caucus with either party.

That hasn’t stopped Democrats from openly supporting him. During the first 16 days of October, after the national spotlight on him had intensified, Osborn raised more than $3 million, almost all of it from individuals and the bulk of it through Democrats’ Act Blue fundraising site, Federal Election Commission reports show. That was almost six times the $530,000 that Fischer raised.

Osborn has raised nearly $8 million total to Fischer’s $6.5 million, and with a little less than three weeks before the election, he had $1.1 million cash, twice what Fischer had.

Osborn has succeeded not only by rejecting political parties but through boots-on-the-ground campaigning across the state, backed by clever ads — in one he notes “I don’t even own a suit” — that contrast his working-class roots with a system where he says politicians “are bought and sold.”

Osborn is a U.S. Navy and Nebraska Army National Guard veteran and industrial mechanic who gained national recognition three years ago when he successfully led a labor strike at Kellogg’s cereal plants, winning higher wages and other benefits. That background shapes his view that working families are being steamrolled by a growing wealth gap, he says.

A win by Osborn would be a giant upset in a state where Republicans hold all statewide offices and all congressional districts.

Fischer is a rancher from Valentine, a town of 2,600 people in northern Nebraska about 300 miles (483 kilometers) northwest of Omaha. She was a little-known state legislator when she ran as an outsider in 2012, winning a competitive primary and then defeating Bob Kerrey, a former Democratic governor and U.S. senator. Her campaign ads that year showed her leaning up against fence posts and called her “sharp as barb wire, tougher than a cedar fence post.”

“Nebraskans support me because I’ve delivered results,” Fischer said this week, mentioning national defense and road projects as areas where she’s done right by her state. “I have a long, conservative record that’s helped build Nebraska and keep America strong.”

Fischer’s pollster, John Rogers of Torchlight Strategies, a longtime national Republican Party operative, argued recently that the apparent closeness of the race is a “mirage.” Her campaign expects that Osborn won’t be able to build a big enough margin in Democratic areas of Omaha, the state’s largest city, to overcome the votes Fischer will win in the vast rural areas.

The pollster also predicted that Trump’s endorsement of Fischer in September will pull Nebraska voters back into her corner in a state he is expected to win handily. “SHE WILL NOT LET YOU DOWN!” Trump posted on his Truth social media site.

Trump labeled Osborn as “Radical Left” and likened him to Vermont Sen. Bernie Sanders, who runs as an independent but caucuses with Democrats and has become a leading spokesman for liberals. Fischer and her supporters reinforce that message.

Still, Osborn has gotten national attention, complicated Republicans’ ambitions and buoyed calls to break up the nation’s two-party system. That has broad appeal in an era when disgust for politics keeps rising.

“At least as an independent, you’re an open book,” said Jim Jonas, who managed Greg Orman’s high-visibility independent U.S. Senate campaign in neighboring Kansas a decade ago. “You have the opportunity to go frame yourself, frame the race and run as a refreshing, different choice rather than the two broken parties.”

That’s exactly how Osborn is pitching himself.

“Congress is a complete misrepresentation of the demographics of our voters,” he told the crowd in Beatrice. “Less than 2% of our elected officials in both the House and Senate come from working-class people.”

Osborn has received donations from political action committees that back independents, like the Wyoming-based Way Back PAC, along with groups supporting Democratic candidates.

His independence hasn’t kept immigration from becoming a key issue, just as it has all over the country. Osborn has said the U.S. border with Mexico is too porous. But he also says he favors some form of amnesty for immigrants in the U.S. illegally for a long time if they’re working and have not committed violent crimes.

Just as Orman did in 2014, Osborn supports abortion rights. That could help him in the aftermath of the Supreme Court’s decision to overturn the constitutional right to an abortion. Voters in seven states, including some conservative ones, have either protected abortion rights or defeated attempts to restrict them in statewide votes over the past two years. Fischer has alleged that Osborn won’t support any restrictions.

But the core of Osborn’s appeal to his backers appears to be as a working-class everyman.

He is getting support from at least a dozen labor unions. Two weeks before the election, the national AFL-CIO brought in top officials to Omaha to lead a phone bank in support of Osborn. Around 30 union members and officials — including AFL-CIO President Liz Shuler — worked the phones to secure support and donations for Osborn.

“His message of backing working families is really resonating with people,” Shuler said.

As she spoke, phone bank volunteers nearby shouted out donations of up to $3,000 and fresh promises of support from Nebraskans they were calling.

“People now are so cynical about politics,” Shuler said. “And he’s getting traction with those people because he’s one of them.”