WASHINGTON (TND) — Hunter Biden's business dealings have long been under investigation and Thursday, House Republicans used that information when they launched a formal impeachment hearing against his father, President Joe Biden.

The chair of the House Oversight Committee, Rep. James Comer, R-Ky., laid that out as one of the central questions.

What were the Bidens selling to make all this money?" he asked at the beginning of the first hearing on Capitol Hill.

Oversight Committee Chairman James Comer, R-Ky., speaks during the House Oversight Committee impeachment inquiry hearing into President Joe Biden, Thursday, Sept. 28, 2023, on Capitol Hill in Washington. (AP Photo/Jacquelyn Martin)

Comer and others have long arguedHunter Biden had little experience, or power, to earn positions on the boards of companies like Burisma Energy in Ukraine, or CEFC in China, and that he was instead paid as a sort of a middleman between the company and Joe Biden, who was then serving as vice president.

“Whether it was lunches, phone calls, White House meetings, or official foreign trips, Hunter Biden cashed in by arranging access to Joe Biden, the family brand," saidRep. Jason Smith, R-Mo., chair of the House Ways and Means Committee, who took part in the hearing.

FILE - President Joe Biden, and his son Hunter Biden arrive at Fort McNair, June 25, 2023, in Washington. (AP Photo/Andrew Harnik, File)

For months, GOP lawmakers have insisted the firing of Ukrainian prosecutor Victor Shokin in 2016 was not for reasons of corruption as Biden and others have said, but because Shokin was investigatingBurisma.

Critics are accusing Republicans of using emails and other messages from when Joe Biden was neither in office, nor a candidate, as evidence of his wrongdoing.

Oversight Committee Chairman James Comer, R-Ky., right, and Ranking Member Rep. Jamie Raskin, D-Md., speak during the House Oversight Committee impeachment inquiry hearing into President Joe Biden, Thursday, Sept. 28, 2023, on Capitol Hill in Washington. (AP Photo/Jacquelyn Martin)

If Republicans had a smoking gun or even a dripping water pistol, they would be presenting it today, but they’ve got nothing on Joe Biden," saidRep. Jamie Raskin, D-Md., ranking member of the Oversight Committee.

Even a key Republican witness said while an inquiry was warranted, the burden of proof has not yet been met.

Witnesses are sworn in before the House Oversight Committee impeachment inquiry into President Joe Biden, Thursday, Sept. 28, 2023, on Capitol Hill in Washington. From left are, Jonathan Turley, Shapiro Chair for Public Interest Law at the George Washington University Law School, Eileen O'Connor, former Assistant Attorney General at the Department of Justice, Bruce Dubinsky, with Dubinsky Consulting, and Michael Gerhardt, Burton, Craige Distinguished Professor of Jurisprudence, University of North Carolina at Chapel Hill. (AP Photo/Jacquelyn Martin)

"I do not believe that the current evidence would support articles of impeachment," Jonathan Turley, chair of Shapiro Public Interest Law and George Washington University law professor, said. "That is something that an inquiry has to establish."

On the Senate side, Republicans spent years on the Hunter Biden matter and published a report on their findings, just before the 2020 election.

The Department of Justice has also investigated and recently indicted Hunter Biden.

And House Republicans have also been looking, as well, since taking the majority in 2022.