Republicans are worried they might lose one more big special election right before the midterms – and a nasty proxy war between the establishment and hardline wings of their party isn’t making them feel any better.

Former Rep. Pat Tiberi (R-OH), a top GOP establishment figure, is fighting like hell to help his hand-picked successor, state Sen. Troy Balderson (R), win his Tuesday primary. But Tea Party conservatives led by former House Freedom Caucus Chairman Jim Jordan (R-OH) have gone all-in to add another member to their bloc of hardliners, with most backing Melanie Leneghan in the crowded field.

Republicans both in the state and nationally are bracing for a difficult August special election in the GOP-leaning district, which includes parts of Columbus and its well-educated suburbs, as well as more rural territory. President Trump won the district by 10 percentage points in 2016, a smaller margin than in some other places Democrats have won special elections in the past year. And GOP strategists say a tough fight would get even harder if Leneghan is their nominee.

“It’s going to be competitive, like a lot of suburban Republican seats around the country, regardless of who the nominee is because of the blue wave that’s coming. Add into that a nominee that’s well outside the mainstream of the party and that’s a recipe for disaster,” said John Weaver, a senior adviser to Ohio Gov. John Kasich (R).

In an unusual move, Tiberi has spent almost a half-million dollars from his own campaign account to boost Balderson. He’s been backed by Defending Main Street, a centrist GOP group with Ohio ties, as well as another Republican super PAC that has ties to House GOP leadership.

On the other side is Jordan, who has come in hard for Leneghan, and the fiscally conservative Club for Growth, whose super-PAC has been spending heavily on ads attacking Balderson.

Tiberi is close to both former House Speaker John Boehner (R-OH) and Republican Ohio Gov. John Kasich, who used to hold this House seat, and the race may be the final salvo in the long-running feud between Jordan and Boehner’s allies, many of whom have left or are leaving office. Jordan led the charge to force Boehner from the speakership in 2015, and he helped fellow hardliner Warren Davidson (R-OH) win Boehner’s old congressional seat. He compared this race to that primary.

“We want someone who’s going to take on the swamp and help President Trump get done what we told the American people we’re going to get done,” Jordan told TPM. “Melanie’s the right person, she’s a fighter, she’s not afraid.”

Democrats have been outperforming their normal numbers in almost every special election this year, making previously safe districts look competitive. While Rep. Conor Lamb’s (D-PA) recent special election victory in a heavily conservative southwestern Pennsylvania district is their only actual House pickup, they’ve won some other major races across the country, and all signs point to a huge enthusiasm gap heading into the midterms. Another special election loss for Republicans would deal their party a psychic blow — as well as bring Democrats one seat closer to the majority (though whoever wins this election is in for a rematch in November).

“If we heaven forbid were to lose this, it sets the narrative of what might be coming even more. We’ve got to put ourselves in a position to stave off another PA-18,” said former Ohio Republican Party Chairman Matt Borges. “Leneghan could be the kind of candidate who could force us into a real hard fight.”

National Republicans concede the August special election is shaping up to be a tough fight for them, and say a Leneghan nomination would further fuel their problems.

“It’s going to be a competitive race,” said one GOP strategist closely following the election. “The candidate that comes out of there would definitely affect how much attention is given by the national parties.”

Both Balderson and Leneghan have been bear-hugging Trump in the primary. But Leneghan is more closely aligned tonally to the president, while Balderson has long been a Kasich ally in the statehouse — an problematic position to be in given how unpopular the anti-Trump governor has become with the state’s GOP base.

Balderson’s vote to help Kasich expand Medicaid coverage in the state is particularly hurtful in the primary — and has been the focus of the Club for Growth Action’s $200,000 worth of ads attacking him.

“His vote to expand Medicaid was definitely noxious to us,” Club for Growth Vice President Andy Roth told TPM. “Obamacare is not popular among Republican voters. Neither is John Kasich in Ohio.”

Democrats have a crowded primary field as well, though strategists say Franklin County Recorder Danny O’Connor is the front-runner in their race.

Columbus and its suburbs have trended toward Democrats for years, but this gerrymandered district shouldn’t be anywhere near competitive in a normal year. And Republicans say a loss there could portend bigger losses this fall.

“It’s big, there’s no question about it,” former Columbus Mayor Greg Lashutka (R) told TPM. “Losing that seat changes the equation.”