Kansas Rep. Tim Huelskamp, a member of the conservative House Freedom Caucus who repeatedly clashed with Republican House leadership, lost Tuesday’s primary to a local physician.

Huelskamp, first elected to Congress in 2010, lost to Roger Marshall by a large 13-point margin in a year that has seen just four House incumbents toppled. Marshall will likely win the general election in November to represent the 1st Congressional District, as the district is heavily Republican and there is no Democratic challenger.

Huelskamp is just the fourth congressional incumbent to lose in this year of the outsider. The other lawmakers to go down are Pennsylvania Rep. Chaka Fattah (D), who is under federal indictment, and GOP Rep. Renee Ellmers (N.C.) and Rep. Randy Forbes (Va.). Both Ellmers and Forbes ran for reelection in new districts after their former districts were redrawn. But Huelskamp is the first to lose a primary outside of those unusual circumstances.

The Huelskamp race became a symbol of the civil war raging between the establishment and anti-establishment wing of the GOP, with the former emerging victorious — this time.

“The establishment forces may have won the battle, but it could cause the House Freedom Caucus to broaden the war,” said Nathan Gonzales, editor of Rothenberg & Gonzales Political Report, which tracks U.S. House and Senate races (Stuart Rothenberg is a PowerPost contributor). “Now I think there’s the possibility that the Freedom Caucus starts supporting challengers to incumbents rather than sticking to open seat races.”

Marshall was the candidate favored by the establishment, and it’s unclear if his win portends anything larger for Republican House members who many fear will be damaged by the presidential candidacy of Donald Trump. So far during the primary season, worries that angry voters would boot out incumbents have not materialized.

“There are unique circumstances to Huelskamp’s race that aren’t easily duplicated to other districts,” Gonzales said. “He was a particular thorn in the leadership’s side and had drawn so much attention to himself to make himself a target, whereas other Freedom Caucus members are not viewed as leading agitators.”

In an interview Wednesday, Huelskamp took aim at the Chamber of Commerce and ESAFund, the super PAC that aired ads opposing his reelection, saying outside spending swayed the election.

“I’m confident if it was just me versus our opponent, we would’ve won,” he said. “The super PACs came in and bailed him out. The moneyed class, the Washington cartel came after me and they got me.”

The race became increasingly close in the final weeks leading up to the primary, as well-funded conservative and business groups poured in $1.5 million to shape the outcome.

Marshall drew support from the U.S. Chamber of Commerce and ESAFund, the affiliated super PAC of billionaire TD Ameritrade founder Joe Ricketts, whose family owns the Chicago Cubs. The group spent $1 million on radio, television and newspaper ads against Huelskamp and for Marshall. And the Chamber put out its own ad endorsing Marshall, and criticizing Huelskamp as an “ineffective obstructionist.”

“Incumbents very rarely lose, which tells us that voters are demanding that Republicans in Congress work together to advance a fiscally conservative agenda to actually end out-of-control spending, not just grandstand,” said Brian Baker, president of ESAFund, previously known as Ending Spending.

Huelskamp’s defeat is a loss for Koch-supported groups Freedom Partners and Americans for Prosperity, which had rallied to aid Huelskamp’s reelection by knocking on doors in the district urging voters to support the congressman. It marked the first time the two groups worked to try to reelect an incumbent in a contested Republican primary this election. The conservative Club for Growth also jumped in, spending about $400,000 on ads backing Huelskamp.

“We remain disappointed that there was so much misinformation put out by some groups that claim to be advocates of limited government and fiscal responsibility,” said Mark Holden, general counsel of Koch Industries and a board member of AFP and Freedom Partners. “These groups falsely claimed Huelskamp was a Washington insider or somehow not a champion on fiscal responsibility and fighting against corporate welfare. We also are disappointed that the resources expended on this race weren’t available to be used in key Senate races.”

Huelskamp drew the ire of business groups and the Kansas Farm Bureau by voting against the Export-Import Bank and the farm bill. He was removed from the House Agriculture and Budget committees in 2012.