This article originally appeared in The Guardian.

Breathless coverage of the presidential horserace has begun, and it seems all but inevitable: We’re heading toward a Trump-Biden rematch. Democrats need to maintain their razor-thin Senate majority if they hope to enact President Biden’s second-term agenda—or, God forbid, fend off Trump’s.

That prospect hinges on a few incumbents facing tough reelection fights. The most critical, must-win seat belongs to Sherrod Brown, a senator from Ohio.

The son of a doctor father and activist mother, Brown received his political education in union halls in the House district he was elected to represent at the age of 23, and has touted “the dignity of work” ever since. He refused to register for a congressional health care plan for his first 18 years in the US House of Representatives, waiting until everyday Americans had access to a federally subsidized plan, too. He opposed free-trade deals from Presidents Clinton and Obama and proudly called himself a “Labor Democrat” before unions were cool.

Over three terms, Brown has maintained his record as, by one measure, the 12th most progressive member of the US Senate, even as his constituency has grown increasingly more conservative. Brown won a third term in 2018 by seven points in a state that voted for Trump by eight points in the election that came before and the one that came after.

Despite decades in Washington, Brown still strikes Ohioans as not only likable, but familiar. He wears a canary pin on his lapel, given to him by a steelworker to commemorate the struggle for workers’ rights. He loves telling people he drives a Jeep Cherokee made in Toledo. He brags about his wife, the Pulitzer Prize–winning writer Connie Schultz, and his rescue pups, named after Franklin Delano Roosevelt and the labor organizer Walter Reuther. It seems that every profile ever written describes Brown as “rumpled,” “authentic” or “gravelly voiced.”

Unlike his fellow Ohio senator, J.D. Vance, Brown does not just play a populist for the press. When GM shuttered its Lordstown, Ohio, plant in 2019, putting thousands of autoworkers out of work, Brown called local UAW leaders immediately to help. More recently, he led efforts to expand union protections for Ohioans building electric vehicle batteries.

And while Biden has taken heat for failing to visit East Palestine, Ohio, following the February 2023 train derailment that spewed hazardous toxins into the air and displaced thousands of residents, Brown has visited the town six times. He’s currently urging the White House and Fema to issue an emergency declaration to get residents recovery resources they desperately need.

As one voter, a 56-year-old veteran who lives outside East Palestine, told The Washington Post: “He’s always around when something is going on.”

That seems to be his MO on Capitol Hill, too. As chairman of the Senate banking committee, Brown has found issues that align his pro-worker philosophy with popular, timely policies—including some that are even palatable to his Republican colleagues. Since the East Palestine disaster, he has partnered with Vance on railroad safety legislation. He is also working with Senator Tim Scott to crack down on fentanyl traffickers and punish failed banking executives by the end of this term.

If Brown’s legislative stock is high, his electoral stakes are even higher.

Democrats have 23 Senate seats up for reelection, and—assuming the vice president, Kamala Harris, is still there to break the tie—they can only lose one to keep their majority. Though Republican operatives in the state admit defeating Brown will be a “dogfight,” current polls have him up by just 0.4 percentage points over one possible opponent, Ohio Secretary of State Frank LaRose. Both The Cook Political Report and Larry Sabato’s Crystal Ball call this race a toss-up.

Joe Manchin’s slide to the dark side and Kyrsten Sinema’s wildcard ways leave Democrats no room for error. If Brown loses, and takes the Democratic Senate with him, democracy hangs in the balance. Republicans will be free to appoint extremist judges, and shut down the government if they don’t get their way. And that’s if Biden wins a second term. If he loses, the parade of horrors will be far, far worse.

Unlike fellow endangered conservative-state Democrats like Manchin and the Montana senator Jon Tester, Brown’s record is uncompromising on abortion rights and gun safety. Recent elections have proved that these are winning issues. To capture and grow this coalition, Brown must win reelection.

A fourth Brown term would also show Americans that this pro-union unicorn need not be so unique. Indeed, the Pennsylvania senator John Fetterman eked out his 2022 victory with a model similar to Brown’s: an unkempt, approachable guy from the Rust Belt who looks and talks like someone voters know.

Sherrod Brown is democracy’s canary in the coal mine. If he goes down next year, the country won’t be far behind. Democrats in Ohio and across the country must turn out for Brown—at fundraisers, campaign events, and at the ballot box.

As we dive deeper into the 2024 election season, and the lunacy that will accompany the first presidential rematch since Eisenhower v. Stevenson, the Democratic party must make reelecting Brown its highest priority.