President Joe Biden weighed in for the first time on the ouster of McCarthy, calling on Congress to change the "poisonous atmosphere in Washington" and come together.

"More than anything we need to change the poisonous atmosphere in Washington. You know, we have strong disagreements, but we need to stop seeing each other as enemies. We need to talk to one another, listen to one another, work with one another. And we can do that," Biden urged while delivering remarks on student loans at the White House.

Biden said the GOP will need to "reorganize" and that it might "take some time" to select a new leader.

-ABC's Justin Gomez and Molly Nagle

House Majority Leader Steve Scalise has officially entered the race to replace McCarthy.

The Louisiana Republican, in a lengthy letter to his colleagues on Wednesday, made a pitch for unity as he touted his work as the No. 2 House Republican.

"You know my leadership style I've displayed as your Majority Leader and Whip," he wrote. "I have a proven track record of bringing together the diverse array of viewpoints within our Conference to build consensus where others thought it impossible."

"Our strength as a Conference comes from our unity, and we have seen when we unite as a Conference, we can deliver wins for the American people," he wrote. "Now we need to take those unified positions and work to extract conservative wins from the Democrat Senate and White House by leveraging upcoming deadlines. While we need to be realistic about what can be achieved, if we stay united, we can preserve leverage for the House to secure tangible wins in our impending policy fights."

Rep. Jim Jordan has sent a letter to colleagues announcing his speakership bid.

"We are at a critical crossroad in our nation's history," he wrote. "Now is the time for our Republican conference to come together to keep our promises to Americans."

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

Now-former Speaker McCarthy addressed reporters from Capitol Hill on Tuesday night where he looked back at his years in Republican leadership, touted his record -- and struck an optimistic if ambiguous note about his future.

"I believe I can continue to fight," McCarthy said, while noting that he will not run again for speaker after he lost a historic vote on the motion to vacate earlier in the day.

"My goals have not changed. My ability to fight is just in a different form," he said, later adding, "I'll never give up on the American people. That doesn't mean I have to be speaker."

McCarthy also swiped at the conservative rebels who ousted him from his role -- stressing that they were just 4% of the GOP conference -- and claimed that Gaetz was acting out of a personal sense of grievance in pushing him out, which Gaetz denies.

Despite the defeat he suffered from within his own party, McCarthy sounded largely sanguine about his political career.

He contended that the Democratic minority deciding to vote against him had made a "political decision" that undercut the ability of the House to govern.

"My fear is the institution fell today," he said.

Still, in largely valedictory remarks, he pointed back to work to cut government spending, expand his party's base and increase their majority in Congress, including by electing more women and minorities.

"I feel fortunate to have served the American people," he insisted. "I leave the speakership with a sense of pride, accomplishment and, yes, optimism."

-ABC News' Adam Carlson