U.S. Rep. Mary Miller defeated Rep. Rodney Davis in the Republican primary for Illinois’ 15th Congressional District on June 28, 2022. With 91% of precincts reporting, Miller had received 57.2% of the vote to Davis’ 42.8%.

This race was one of six U.S. House incumbent-vs.-incumbent primaries occurring in 2022 as a result of congressional redistricting.

The Herald & Review‘s Brenden Moore wrote that the race was “among the most contentious incumbent-versus-incumbent primaries in the country” and said the candidates “traded barbs over who [was] the true conservative candidate in the race.” As of election day, the primary had the second most satellite spending of all 2022 U.S. House races.

Miller said she was the “only Republican member of Congress from Illinois who’s fighting every aspect of the Biden agenda and putting America first,” saying on her campaign website that she had opposed “the disgraceful January 6th ‘witch hunt’ Commission, President Biden’s ‘red-flag’ gun confiscation measures, COVID vaccine mandates and databases, and taxpayer-funded chemical abortion.” She criticized Davis for a bill he cosponsored in 2019 that would have provided grants for states to enact extreme risk protection order laws, or red flag laws. Miller said, “I am the only candidate with an A rating from the NRA and Gun Owners of America because I support our Second Amendment! Everyone is tired of Red Flag Rodney Davis, who stabbed conservatives in the back by supporting federal gun confiscation.”

Former President Donald Trump (R) endorsed Miller in January 2022. U.S. Sen. Ted Cruz (R-Texas), Club for Growth, the Conservative Political Action Coalition, and the House Freedom Fund also endorsed Miller.

Davis said, “I stick with my core values and principles. I have always been pro-life and will continue to stick by those values and principles. I’ve always stood up for the Second Amendment. I will continue to do that. But what separates me from my opponent is I have a record of actually governing. When people put Republicans in charge, at any level of government, they actually expect them to do the job.” Davis criticized Miller for voting against the 2022 National Defense Authorization Act, saying, “All Mary Miller has to show for her time in Congress is quoting Hitler and voting with Democrats like [Alexandria Ocasio-Cortez] and the far left squad to defund our military and block a pay raise for our troops. That’s shameful. It’s clear that Mary Miller is all talk, no action.”

The U.S. Chamber of Commerce, Illinois Farm Bureau, and Illinois Fraternal Order of Police State Lodge endorsed Davis, along with U.S. Reps. Mike Bost (R-Ill.) and Darin LaHood (R-Ill.).

Davis has represented Illinois’ 13th Congressional District since 2013, and Miller has represented the 15th Congressional District since 2021. According to data from Daily Kos, 28% of the new 15th District’s population came from the old 13th District (represented by Davis), and 31% came from the old 15th District (represented by Miller). Illinois lost one congressional district following the 2020 census.

Major independent observers rate the general election as solid or safe Republican.