(Bloomberg) -- Republican firebrand Matt Gaetz has invoked a rare parliamentary maneuver — one that hasn’t resulted in an actual floor vote in more than a century — in his campaign to oust Speaker Kevin McCarthy. 

Gaetz made good on his longstanding threat to topple McCarthy on Monday, going to the well of the House to trigger a “motion to vacate the chair,” setting a roughly two-day time limit for a test of the House leader’s support. 

To succeed in stripping McCarthy of his gavel, Gaetz needs support from a simple majority of all House members who cast a yes or no vote — Republican and Democrat.

The backroom maneuvering is complicated, and potential scenarios are varied. If House Democrats led by Hakeem Jeffries were to vote in unity to oust McCarthy, Gaetz would then only need four other Republican hardliners to join him in the mutiny.

But Democrats could also come to the Republican speaker’s rescue — even without formally opposing his ouster. They could just sit out the removal vote, or vote “present” — lowering the number of overall votes McCarthy needs to reach a majority and providing a buffer against five or more of his GOP colleagues voting to remove him.

Read More: Republican Gaetz Moves to Formally Remove McCarthy as Speaker

Democrats could also join with the more than 200 solid McCarthy allies in the House to support parliamentary maneuvers to block the effort, such as laying the ouster on the table or referring it to a committee.

Democrats plan to meet early Tuesday to discuss the motion.

The motion to vacate dates to a parliamentary rules manual written by Thomas Jefferson. The tactic was last used to force a floor vote in 1910 against then-Speaker Joseph Cannon and failed. 

But just the threat of being removed through this process has caused anxiety for more-recent GOP speakers, including John Boehner and Paul Ryan. In 2015, Boehner resigned when ultra-conservatives threatened an ouster attempt rather than rely on Democratic support to stay in power.

Gaetz’s announcement of his challenge to McCarthy on the House floor requires McCarthy to put the matter on the floor for consideration within two “legislative days.” 

Legislative days typically line up to calendar days when the House is in session. But there is some opportunity for gaming the deadline, since they technically run from when a session is opened to adjournment. Speakers can — and have in the past — kept the same legislative day going by avoiding adjournment and could theoretically do so for weeks or even months.

If the motion to remove McCarthy passes, a interim speaker would preside over a new speaker election. 

Just as in January, when it took 15 ballots to elect McCarthy, the House would accept nominations from both parties and take as many votes as necessary until someone wins a majority of members voting.

No other candidates have, for now, emerged publicly for McCarthy’s job, but the names of the No. 2 House Republican, Steve Scalise of Louisiana, and the No. 3 Republican, Tom Emmer of Minnesota, have been raised.

Also, nothing prevents McCarthy from running again.

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