The former chief of staff to Rep. Nancy Mace (R-S.C.) on Friday filed to run as a Republican primary challenger against his onetime boss.

Why it matters: It sets up what could be a high-profile primary after Mace angered and perplexed some in her party by voting to oust former House Speaker Kevin McCarthy (R-Calif.) last October.

Driving the news: Daniel Hanlon filed to challenge Mace in the state's June congressional primary on Friday, according to a Federal Election Commission filing.

• Hanlon worked as a senior staffer for Mace from when she first entered Congress in 2021 until last December, including as chief of staff for nearly two years, according to LegiStorm.
• He previously worked for former Rep. Mick Mulvaney, another South Carolinian, as well as former Arizona Rep. Rick Renzi.
• Mace declined to comment on Hanlon's entry into the race. Hanlon did not immediately respond to a request for comment.

The backdrop: Mace has built a high-profile reputation in Congress as someone who has bucked her party in unpredictable ways, taking both moderate and conservative positions.

• She angered former President Trump and his supporters by opposing 2020 election objections and voting to hold Steve Bannon in contempt of Congress, and has also criticized the GOP for its firmly pro-life policies.
• But Mace has also sided with right-wing hardliners in voting to oust McCarthy and by opposing government spending bills.
• Recent reports have drawn attention to her struggle to retain staffers and her appetite for the public spotlight.