As bad as Joe Biden's presidency has been thus far, it's about to get a whole lot worse.

In a letter to federal law enforcement officials last week, Sen. Charles Grassley (R-Iowa) noted that the FBI is likely in possession of "significant, impactful, and voluminous evidence" of "potential criminal conduct by Hunter Biden and James Biden," Joe Biden's brother.  Moreover, he added, the president himself "may have been involved."

The letter, sent to Attorney General Merrick Garland, FBI Director Christopher Wray, and Delaware U.S. Attorney David Weiss — who is running the ongoing criminal investigation into Hunter Biden — contained whistleblower allegations that relate to Hunter and James Biden's dealings with CEFC China Energy, an energy conglomerate linked to the Chinese government. In addition, the documents also relate to Hunter Biden's 'work' on the board of Ukrainian gas giant Burisma Holdings, according to the Washington Examiner, which obtained a copy of Grassley's letter.

The Iowa Republican said his staff "reviewed the unclassified records" that support claims made by the whistleblower.

"Based on recent protected disclosures to my office, the FBI has within its possession significant, impactful, and voluminous evidence with respect to potential criminal conduct by Hunter Biden and James Biden," Grassley, the ranking member on the Senate Judiciary Committee, wrote.

Included in the evidence that Grassley cited is an interview the FBI conducted in October 2020 with former Biden family business associate Tony Bobulinski. In his letter, Grassley said that Bobulinski told federal agents that Hunter Biden and James Biden were working with foreign nationals linked to the Chinese Communist Party on "potential business deals and investments while Joe Biden was Vice President; however, that work remained intentionally uncompensated while Joe Biden was Vice President."