What the Mike Bost, Darren Bailey election results tell us about the Republican Party

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U.S. Rep. Mike Bost has defeated former state senator Darren Bailey in the closely-watched March 19 primary race for southern Illinois’ 12th Congressional District, according to unofficial returns.

The Associated Press called the race at 9:14 a.m. Wednesday, with 98% of the votes reported. On Tuesday night, with about 20% of votes still being counted, Bost declared victory and Bailey conceded.

On Wednesday, Bost was leading by 2.8 percentage points, with 2% of the vote still not counted:

  • Bost: 48,493 votes, or 51.4% of the votes.

  • Bailey: 45,903 votes, or 48.6% of the votes.

Counties may receive additional mail-in ballots until April 2. The results are unofficial until local election authorities complete their canvass of results next month.

People across the country watched the 12th District primary race, which pitted two conservative, ex-President Donald Trump supporting Republicans against each other.

Bost, R-Murphysboro, has been the 12th District’s representative for five terms.

Bailey, R-Xenia, served in the Illinois House for one term and in the Illinois Senate for one session before running for governor in 2022. Bailey won the Republican gubernatorial primary but ultimately lost to Democratic incumbent J.B. Pritzker.

It’s noteworthy that Bailey would garner a percentage of the vote in the upper 40s in a race where Bost had so many advantages: Bost is the incumbent, he had the support of the party leadership to aid his campaign with cash and troops on the ground and, perhaps most importantly, he had Trump’s endorsement.

It could signal that Bailey’s uncompromising approach resonated with voters and may be where the Republican Party is heading, according to political analyst John Shaw, the director of the Paul Simon Public Policy Institute at Southern Illinois University Carbondale.

Bost and Bailey’s campaign comes amid growing division within the Republican Party, often led by arguments against compromise from its far-right members.

“Darren Bailey is running unabashedly as a candidate of disruption whereas Rep. Bost has been trying to position himself as a so-called governing conservative,” Shaw said ahead of Tuesday night’s results. “It’s unclear what the Republican Party really wants right now.

“With their continuing embrace with Donald Trump, they’re very comfortable with the politics of disruption,” Shaw added.

Importance of 12th District primary

Bost and Bailey share many of the same views on issues they see facing the state and the nation, including gun rights and immigration reform. But during the campaign, Bailey’s attacks on Bost’s record showed how he would do the job differently.

Bailey opposed two immigration reform proposals from Bost’s tenure, for example, because they included pathways to citizenship for people who entered the U.S. without legal permission, even when those proposals included other provisions Bailey supports, like building Trump’s border wall.

Bost describes himself as a governing conservative, which means he is willing to work with colleagues to reach a compromise.

Bailey criticized Bost for making concessions, promised voters he wouldn’t budge on conservative platform issues and aligned himself with Republican U.S. Reps. Matt Gaetz of Florida and Mary Miller, who represents Illinois’ 15th Congressional District.

Gaetz and Miller endorsed Bailey in the 12th District race over Bost, their colleague in the House. They are both members of the influential and ultraconservative House Freedom Caucus. The group’s members led the first removal of a House speaker in history, which put GOP leadership in turmoil and halted work for weeks in October. Freedom Caucus members have also been among the main opponents to compromises involving government spending and border security.

Bost, on the other hand, had the support of Republican Party leadership, including House Speaker Mike Johnson and House Republican Conference Chairwoman Elise Stefanik.

Bost’s win with a slim majority of Republican voters in the 12th District ultimately signals they’re comfortable with a candidate who has strong conservative values but is also trying to keep the government open and programs functioning, according to Shaw. Still, a significant amount of voters showed they want something different with a vote for Bailey.

Bost’s victory statement on Tuesday night referenced the fracturing GOP.

“I’m hopeful we can work to reunify our party in advance of a critical general election,” Bost stated.

In his concession speech, Bailey said conservative principles are “constantly challenged and must be defended with vigor.” He called on Republican voters to unite behind Trump in November. Bost also expressed support for Trump on election night, referring to him as the country’s next president in the victory statement.

A contentious campaign

On the 2024 campaign trail, Bost and Bailey regularly traded attacks.

Bost touted his experience and seniority in the U.S. House as an asset, noting he received important committee assignments like veterans’ affairs and agriculture, while Bailey framed it as a liability by labeling Bost a Washington insider.

Bailey highlighted the small-donor donations funding his campaign and accused Bost of being supported by special interest groups.

Bost fired back by describing Bailey as a career candidate continuously running for office because he’s motivated by ego.

The candidates also publicly debated their support for Trump and privately fought for his endorsement in the race.

Trump had previously endorsed both of them in their races during the 2022 general election: Bost for re-election to the 12th District and Bailey for governor. But in their matchup for the 12th District, Trump threw his support behind Bost in late February, a fact Bost highlighted in television ads during the campaign.

And for some 12th District voters, Trump was the factor that determined how they cast their vote.

On Tuesday afternoon at the only polling place in Freeburg, a handful of voters told the BND they picked Bost because he was the Trump-endorsed candidate. But another voter said they picked Bailey because his campaign signs promised he “fights like Trump.”

“Out of the two, I think Trump is more on Bost’s side than Bailey,” 25-year-old voter Caleb Greason said of how he chose between the candidates.

Bost hasn’t had a primary challenger since 2018, when he defeated Preston Nelson with 84% of the vote. (Nelson ran for the 12th District again in 2024 as a Democrat.)

Bost faced a greater challenge with Bailey. The former state legislator made a name for himself opposing COVID-19 pandemic restrictions. And the 12th Congressional District supported his run for governor; Bailey took more than 70% of their vote in the 2022 gubernatorial primary.

In this race, primary results are especially important because the 12th District is solidly Republican, so its congressman is effectively chosen in the GOP primary rather than the general election when candidates from both parties are on the ballot.

Democrat Brian Roberts will face Bost in the Nov. 5 general election, according to the unofficial primary results.

BND visual journalist Joshua Carter contributed information to this report.