WASHINGTON — Steve Ricchetti, a former high-ranking aide to ex-President Joe Biden and a member of his so-called “Politburo,” provided testimony to the House Oversight Committee affirming that Biden was “fully capable” of fulfilling his responsibilities and that no one “usurped” his authority as president.

Ricchetti, aged 68, who previously served as counselor to the president and remains a dedicated supporter of Biden, appeared before the Republican-controlled panel for approximately eight and a half hours on Wednesday. This was part of an inquiry into the 46th president’s cognitive abilities and the use of autopen.

In his opening statement, Ricchetti asserted, “Let me be clear: At all times during his presidency, I believed that President Biden was fully capable of exercising his Presidential duties and responsibilities, and that he did so. Neither I, nor anyone else, usurped President Biden’s constitutional duties,” according to multiple reports.

“I firmly believe that at all times during my four years in the White House, President Biden was fulfilling his constitutional duties. Did he stumble? Occasionally. Make mistakes? Get up on the wrong side of the bed? He did – we all did.”

Ricchetti is now the seventh Biden confidant to come before the panel and claims he did so voluntarily to combat the “false narrative that President Biden was mentally unable to perform his Constitutional duties.”

The 68-year-old has long been in Democratic politics, having worked on Biden’s campaign, served as his chief of staff during the latter half of his vice presidency, and as the White House deputy chief of staff for operations in the Clinton administration.

For four years, Ricchetti played a critical role in shepherding Biden’s legislative agenda.

In the book “Original Sin,” Ricchetti was described as one of five members in Biden’s core inner circle, dubbed the “Politburo” and described as the “ultimate decision-makers” surrounding the 46th president.

At one point, Ricchetti personally rang up a reporter to push back against claims from multiple sources about Biden’s condition, according to the book.

He also railed against actor George Clooney in the wake of the actor’s stunning op-ed against Biden last July.

“Ricchetti read it and was furious. Internally, he threatened to shut Clooney down—some of his colleagues thought he sounded like a mob boss,” authors Alex Thompson and Jake Tapper recounted.

Back in May, Oversight Committee Chairman James Comer (R-Ky.) began blasting out requests to former Biden aides to assist in a probe of the former president’s use of autopen to sign key documents and whether they helped participate in a “cover-up” of his mental cognition.

Ricchetti was summoned for testimony last month.

Behind closed doors on Wednesday, Ricchetti took aim at the GOP-led Oversight panel, accusing it of participating in a “concerted effort by the Administration and its Congressional allies to diminish the record of the former President.”

“I am not aware of any effort to use the autopen on important documents without the President’s knowledge and consent,” Ricchetti added in his opening statement. “I am not aware of any effort to keep important information from the President.”

“Senior White House staff kept the President fully informed so that he could provide direction and make all important decisions.”

Biden, for his part, declared in a statement provided by his office that “I made the decisions about the pardons, executive orders, legislation, and proclamations.”

“Any suggestion that I didn’t is ridiculous and false.”

Asked about Ricchetti’s testimony, Comer indicated that the Biden official was not very forthcoming.

“He didn’t tell us a whole lot of what you wouldn’t expect,” the Kentucky Republican told Fox News “Ingraham Angle” host Laura Ingraham.

“His testimony wasn’t consistent with others who have actually testified,” Comer added, noting that about half the former White House officials the committee has brought in have asserted their Fifth Amendment rights.

“All their testimony is inconsistent,” Comer continued. “So we’re going to put the pieces together, and we’re going to release all the transcripts, and we’re going to issue a report, and hopefully we’ll be able to determine whether or not Joe Biden had any idea who was using the autopen and what they were using it for.”

The Trump administration has opened multiple probes into Biden’s use of autopen that dovetail with the Oversight Committee’s work.

Other aides to appear before the powerful investigative panel, including former White House Chief of Staff Ron Klain; Jill Biden’s powerful former chief of staff Anthony Bernal; former presidential physician Dr. Kevin O’Connor; Ashley Williams, former special assistant to the president and deputy director of Oval Office Operations; and Neera Tanden, the former White House director of the Domestic Policy Council.

Several of the Biden aides have pleaded the Fifth Amendment and declined to answer questions from the Oversight Committee.

The powerful investigatory panel is slated to hear from former senior adviser Mike Donilon on Thursday.