Herrig noted in his letter that under House Rule 25, members of Congress have to first have any members receive authorization from the Ethics Committee before they can reap financial rewards from copyright royalties like those for a typical book publishing contract.

"As Representative Comer continues to hold hearings and attempts to build the case to impeach President Biden, the American people deserve to know the extent to which he is benefiting financially," the letter continued. "It is clear already that he has a political motive to impeach the President and it should be revealed if he has a financial motive as well."

The New Republic reported that Comer has admitted that actual articles of impeachment are not likely from his committee, and that the most Republicans could expect would be a criminal referral to the Department of Justice. And while DOJ special counsel David Weiss is already investigating Biden's son, Hunter, for alleged tax-related crimes, an additional indictment of Biden himself is unlikely to emerge from any referral by the Oversight Committee.

"Recent reporting revealed that Representative Comer has been in talks with at least one publisher regarding a book on his impeachment inquiry into President Biden," Herrig wrote in his letter, adding that "Representative Comer and his Republican colleagues have spent the past 15 months relentlessly investigating the president and his family and failed to find any evidence of wrongdoing by President Biden let alone anything impeachable."

Comer's attempt to have Biden impeached was largely based on allegations within an FBI informant report in which Biden and his son were said to have solicited $10 million in bribes from the Ukrainian government. However, the author of that report, 43-year-old Alexander Smirnov, was later indicted for lying to the FBI about those allegations.

Smirnov was also subsequently indicted for attempting to flee prosecution. The disgraced former FBI informant was alleged to have had contact with "high-ranking" members of Russian intelligence agencies who sought to sow disinformation ahead of the 2024 presidential election.

Former Rep. Ken Buck (R-CO), who left Congress last month after a surprise early retirement announcement, admitted Smirnov's indictment essentially rendered the GOP's efforts to impeach Biden fruitless.

"We were warned at the time that we received the document outlining this witness' testimony — we were warned that the credibility of this statement was not known," Buck told CNN host Caitlan Collins. "And yet, people — my colleagues — went out and talked to the public about how this was credible, and how it was damning. And how it proved President Biden's — at the time, Vice President Biden's — complicity in receiving bribes. It appears to absolutely be false and to really undercut the nature of the charges."