Illinois will hold its primary elections on Tuesday, with eyes on one congressional incumbent facing a challenge from within his party — joining several 2024 contests that have highlighted the fracturing of the Republican Party.

Rep. Mike Bost (R-IL), who represents Illinois’s 12th Congressional District, is facing a challenger from the party’s hard-line flank. Though Bost has the incumbent and fundraising advantages, as well as an endorsement from former President Donald Trump, he is facing competition from his own House colleagues as they throw support behind his challenger, Darren Bailey.