Donilon, who has worked with Biden since 1981, entered the Rayburn House Office room at 10:05 a.m. and left the hearing shortly after 4 p.m. He did not respond to questions from reporters.

Donilon has been a staunch defender of Biden since he dropped out of the 2024 presidential race, maintaining during his testimony that he believes congressional Democrats overreacted after Biden’s debate against Trump, according to the source familiar.

The longtime Biden aide confirmed to the committee that he was paid $4 million for Biden’s reelection campaign, and would have been paid another $4 million if Biden had won, the source familiar said.

BIDEN AUTOPEN USE: WHAT TO KNOW AS TRUMP ORDERS AN INVESTIGATION INTO HIS PREDECESSOR

The longtime Biden aide and 2024 campaign adviser is the latest Biden team member to testify before the committee and the second from the so-called “Politburo” group made up of his closest advisers, according to Alex Thompson and Jake Tapper’s book, Original Sin: President Biden’s Decline, Its Cover-Up, and His Disastrous Choice to Run Again. Former deputy chief of staff Steve Ricchetti, who testified Wednesday, was the first from the group to testify.

The source familiar told the Washington Examiner that Donilon admitted Biden’s presence was not as commanding and that he would stumble over more words. Donilon expressed to the committee that he was frustrated over Biden’s perception, but acknowledged the difficulty of overcoming the visuals people have seen of him.

Like Ricchetti, the committee hoped that Donilon’s testimony as a close adviser would shed light on Biden’s mental acuity during his time in the Oval Office, particularly in 2024, when the former president’s autopen signature was used to sign a wave of executive actions and pardons.

Donilon claimed to the committee that he did not recall having any knowledge of the autopen’s use and did not know what it was used for, according to the source familiar.

House Oversight Committee Chairman James Comer (R-KY) sent a letter to Donilon on June 4 requesting his testimony, writing that the committee believes the aide has information “critical” to the investigation.

“If White House staff carried out a strategy lasting months or even years to hide the chief executive’s condition—or to perform his duties—Congress may need to consider a legislative response,” Comer’s letter to Donilon reads.

In his opening statement, Donilon told the committee that what he saw from Biden “day in and day out, was a leader who was deeply engaged and in command on critical issues, both at home and abroad,” according to the Associated Press.

Donilon went on to tell the committee that “every president ages over the four years of a presidency and President Biden did as well, but he also continued to grow stronger and wiser as a leader as a result of being tested by some of the most difficult challenges any President has ever faced,” according to the outlet.

THE LONG HISTORY AND CONTROVERSY OF PRESIDENTIAL AUTOPEN USE

Multiple presidents have been known to utilize an autopen during their time in the White House, usually to sign presidential letters and messages. However, during Biden’s waning hours in office, the tool was used to sign a series of pardons and clemency actions, which were met with skepticism once President Donald Trump reentered the White House.

Trump’s White House counsel launched an investigation earlier this month into the Biden administration’s use of the autopen, in conjunction with the Justice Department.

Donilon is the eighth former Biden official whom the Oversight Committee has interviewed as part of its inquiry. The committee has also scheduled interviews with former deputy chief of staff for policy Bruce Reed on Tuesday, and former senior adviser to the president for communications Anita Dunn on Aug. 7.

BIDEN AUTOPEN USE IN DC WAS MORE WIDESPREAD THAN PREVIOUSLY KNOWN

More former Biden officials are expected to testify over the coming weeks, with interviews for press secretary Karine Jean-Pierre, former Biden communication aides Ian Sams and Andrew Bates, and former chief of staff Jeff Zients, scheduled for August and September.

The Washington Examiner has reached out to Donilon’s lawyer for comment.