Republican Matt Gaetz officially moved to topple House Speaker Kevin McCarthy on Monday, teeing up a high-stakes vote likely to dramatically shift the balance of power in Washington whatever the outcome.

McCarthy’s embrace on Saturday of a bipartisan deal to avert a US government shutdown triggered the Florida Republican’s mutiny.

Gaetz stood in the well of the House, formally launching the process. McCarthy must call a vote within two legislative days.

The move, officially called a motion to vacate the chair, is a parliamentary process that has not resulted in a speaker removal vote since 1910. In that case, then-speaker Joseph Cannon survived the test.

McCarthy responded defiantly, telling CBS News on Sunday he’ll survive any attempt to remove him.

McCarthy needs only a simple majority of House members voting to stop the effort to remove him. Republicans hold a slim majority and just five could join unified Democrats to bounce McCarthy from the speaker’s office.

“If anyone brings a motion to vacate at any time, I will vote for it. I would never vote to retain the speaker,” Virgina Republican Bob Good said on Monday. “What he did on Saturday is overwhelming confirmation of the concerns we had in January.”

Some House Democrats have previously said any effort to save McCarthy from a hardliner revolt would be contingent on bipartisan compromises.

In 2015, then-Speaker John Boehner resigned when hardliners threatened such a rebellion rather than rely on Democratic votes to remain in power.