In a 45-minute roll call vote, the House moved to oust McCarthy as speaker.

The final vote was 216 to 210 in favor of Gaetz's motion to vacate, with eight Republicans joining Democrats.

"The office of speaker of the House of the United States House of Representatives is hereby declared vacant," said presiding officer Rep. Steve Womack.

It is the first time in U.S. history that the speaker of the House has been booted from the post, putting the chamber in unprecedented territory.

Republican rebels appear to have enough votes to remove McCarthy as speaker, given that Democrats joined them, though the vote is ongoing.

The House would be in uncharted waters if McCarthy is removed as speaker: A motion to vacate has never been used successfully.

But the chamber wouldn't be as paralyzed and chaotic as it was in January amid McCarthy's five-day, 15-ballot vote to win the gavel.

As part of a rule change after 9/11 to support the continuity of government, the speaker is required to deliver to the House clerk an ordered list of members who can act as speaker pro tempore in the event of a vacancy.

The person at the top of McCarthy's list will serve as interim speaker until a new one is elected.

If the motion to vacate is successful, the chamber could go right to another speaker vote -- and McCarthy's allies could put him forward again to reclaim his post.

But unlike in January, it's possible that the House could take up other business in the meantime: The chamber has a rules package, and the speaker pro tempore would have the authority to act as speaker until a new one is elected.

A roll call vote is underway on the motion to vacate, which will decide whether McCarthy will keep his gavel.

If successful, it will be a historic moment. The motion to vacate has only been used once before -- more than a century ago -- and failed.

It would take as few as five Republican defections to oust McCarthy as speaker, if all Democrats vote against him.

Senate Republican leader Mitch McConnell said he is keenly aware of the thankless work it takes to be a Congressional leader as he praised McCarthy in a floor speech.

“I’ve said before, in reference to my own position, that being the leader of your party in the Senate is much like being the groundskeeper at a cemetery. Everybody’s under you, but no one’s listening," McConnell said, adding: “Of course, I doubt that Kevin McCarthy has ever seen himself as above anyone else."

McConnell praised McCarthy's willingness to dive "head first" into worthwhile fights, calling him a trusted and honest partner in leading the GOP caucus.

“He didn’t hesitate to get his hands dirty. When circumstances were tough, he drew on his faith, his family and his belief in American exceptionalism," McConnell said.

“And I’m not sure anyone could have predicted just how much these qualities would come in handy over the past nine months," he said.

-ABC's Mariam Khan