“There is evidence of bias, trending toward animus, among those charged with investigating serious cases. There is evidence political opposition research was used in court filings. There is evidence this political opposition research was neither vetted before it was used nor fully revealed to the relevant tribunal,” Goodlatte and Gowdy wrote in their letter.
The idea has the potential to bolster a second, parallel narrative being pushed chiefly by some House Republicans that shifts focus away from the Russia investigation to the motives of the investigators examining those questions.
Democrats criticized the letter Tuesday, accusing Republicans of undermining the Mueller investigation.
"These are blatant attempts to distract from and undermine the credibility of Special Counsel Mueller," Rep. Jerry Nadler, D-N.Y., the top Democrat on the House Judiciary Committee, said in a statement.
Goodlatte said Tuesday that the investigation "involves decisions made at the highest levels of the FBI and high levels of the Department of Justice that need to be examined from the outside."
Gowdy, who is also chairman of the Government Oversight Committee, and a member of the House Intelligence Committee conducting its own Russia investigation, said a special counsel in the executive branch is better-equipped than a divided Congress to probe the allegations.
"Congress doesn’t have the tools, or frankly, the public confidence to conduct these investigations. We leak like the gossip girls," he said. "Congress does not investigate criminality."
In September, Goodlatte and Judiciary Committee Republicans asked Sessions and Rosenstein to appoint another special counsel to look into the FBI's handling of the Clinton email investigation and other matters at the Obama Justice Department. And a smaller group of House Republicans called on Sessions to appoint a second special counsel last month over the FISA surveillance court abuse allegations and the FBI's decision to launch a counterintelligence investigation into the Trump campaign.
Gowdy, who did not sign on to previous efforts, said Tuesday that "this might be the one time Congress is right."
"Even a broken clock is right twice a day," he said of the request.