House Rep. Mike Gallagher, R-Wi., chairman of the Select Committee on the Chinese Communist Party, announced on Saturday that he would not seek re-election this year, leaving a seat open in a key swing state as the 2024 race kicks into high gear.

The former Marine Corps officer joins an exodus of more than a dozen Republican congress members planning to leave their posts, each one widening the path for Democrats to attempt to win back the House majority. His seat in Wisconsin’s 8th congressional district is particularly valuable, given the state’s battleground status and House Republicans’ current rail-thin majority.

“Electoral politics was never supposed to be a career and, trust me, Congress is no place to grow old,” Gallagher said in a statement announcing his departure.

At times, Gallagher has splintered from his party. He was one of three Republicans on Tuesday to buck party leadership and vote against the impeachment of Homeland Security Secretary Alejandro Mayorkas, sinking the motion.

He was also a vocal critic of former President Donald Trump’s involvement in the Jan. 6, 2021, insurrection, though he opposed the impeachment of Trump that followed.

Despite occasional resistance to his party, Gallagher is still an essential GOP vote representing a key swing state. Trump won Wisconsin in 2016 but lost it to President Joe Biden in 2020.

Gallagher’s retirement will likely trigger a congressional frenzy on both sides of the aisle to fill his seat.

Wisconsin’s 8th district is a slightly redder region of the Badger State. In 2022, Gallagher won roughly 72% of the vote against several third-party candidates but no formal Democrat opponent.

This time could be different, though, with Democratic eyes already gearing up to replace him. Kristin Lyerly, a Wisconsin OBGYN, has said she is considering a bid to flip Gallagher’s seat.

Gallagher has served four terms in Congress. His departure from Washington was unexpected given his status as a GOP rising star. Republicans last year eyed Gallagher for a possible Senate run, which he declined.

He was also appointed to the helm of the House’s high-profile China committee, which was created at the start of last year.

The Select Committee on the CCP is a bipartisan group of lawmakers dedicated to oversight and regulation of U.S.-China relations. The committee made news in January when FBI Director Christopher Wray announced that U.S. investigators had targeted and neutralized a Chinese-backed hacking group called “Volt Typhoon.”