Speaker Mike Johnson is about to drop to a one-vote majority, as retiring Rep. Mike Gallagher has decided he will exit the House as soon as next month, according to two people with knowledge of the matter.

The Wisconsin Republican announced earlier this year that he would not seek reelection, which came on the heels of receiving blowback for voting against impeaching Homeland Secretary Alejandro Mayorkas. His allies, however, say he was long jaded by the antics of the House following the ouster of Speaker Kevin McCarthy.

Gallagher’s office did not immediately return a request for comment.

The timing couldn’t be worse for Johnson, who is now potentially facing a vote on his ouster in the coming weeks. Rep. Marjorie Taylor Greene (R-Ga.) filed the so-called motion to vacate on Friday, over Johnson working with Democrats to pass a massive spending bill, but it’s unclear when she’ll try to force the vote on the floor.

It also further fuels conference concerns over its trajectory headed into the November election. Fewer mainstream Republicans like Gallagher means a larger share of GOP hardliners are more empowered to take on their own party.

Since Gallagher announced his retirement, the chair of the Select Committee on China has nabbed a legacy-making moment: House passage of a bipartisan bill that would force TikTok in the U.S. to sever its ties to the Chinese government.

Gallagher has said he plans to continue working on national security issues as part of the private sector.