President Trump’s closest congressional allies said Wednesday that a four-hour interview with former FBI general counsel James Baker had “fundamentally changed” their understanding of the Justice Department’s Russia investigation, confirming and furthering their previous convictions that federal law enforcement agencies were biased in their scrutiny of President Trump’s campaign.

Reps. Mark Meadows (R-N.C.) and Jim Jordan (R-Ohio), both leaders in the conservative House Freedom Caucus, called the closed-door meeting the “most informative” interview they have had in the House Judiciary and Oversight and Government Reform committees’ nearly year-long probe into the FBI’s investigations of the Trump campaign’s alleged ties to Russia and former secretary of state Hillary Clinton’s use of a private email server.

Democrats have repeatedly argued that the Republicans’ aim is to undermine and discredit the FBI and Justice Department, as well as special counsel Robert S. Mueller III’s ongoing probe of Russian interference in the 2016 election. They have also criticized the probe’s format of conducting private interviews, saying that doing so allows Republicans to misrepresent witnesses’ testimony.

Jordan told reporters that Baker informed them of a “completely new” and “explosive” source who provided information “directly” to the FBI “during the time that the DOJ and the FBI were putting together” an application to surveil former Trump campaign adviser Carter Page. He offered no details about the source or the information the source provided to the bureau beyond saying it was “related to the whole Russia investigation.”

Baker declined to comment to reporters as he departed the interview.

The FBI’s press office did not immediately respond to a request to comment on Jordan’s characterization of Baker’s testimony.

Meadows and Jordan have been among Trump’s most dogged defenders as the president seeks to discredit federal law enforcement’s Russia investigations, which Trump has labeled a “witch hunt.” Earlier this year, Meadows and Jordan led a movement to impeach Deputy Attorney General Rod J. Rosenstein for refusing to turn over documents they believed would expose the Mueller investigation’s “rotten foundation,” as Rep. Matt Gaetz (R-Fla.) has described it.

Republican Party leaders’ support for their efforts has ebbed and flowed.

Jordan hinted that Baker’s testimony may have bolstered their complaint that the FBI failed to include in its surveillance application evidence that would have steered suspicion away from Page. It “sheds even more light on just how wrong this whole idea, when they took this dossier to the secret court and did what they did,” he said.

The dossier — a collection of intelligence detailing Trump’s alleged personal and business ties to Russia — has also been a chief focus of GOP lawmakers who say it was the source of the FBI’s entire investigation. The bureau denies that charge, which has also been undercut by reports that Trump campaign aide George Papadopoulos told Australia’s ambassador to Britain that the Russians had dirt on Clinton months prior.

A spokesman for the House Judiciary Committee Democrats did not immediately respond to a request to comment on Jordan’s characterization of Baker’s testimony. Only a handful of lawmakers attended Wednesday’s hearing, as the House is not in session.

In recent weeks, the panel has interviewed individuals who members believe are linked to the dossier’s production and dissemination throughout the intelligence and federal law enforcement communities, including Bruce Ohr, the Justice Department official who spoke with the dossier’s author on several occasions. Later this month, the panel plans to interview Ohr’s wife, Nellie Ohr, who briefly worked as a contractor for Fusion GPS when the research firm was involved with Steele. Fusion GPS founder Glenn Simpson has declined an invitation to meet with the panel. House Judiciary Committee Chairman Rep. Bob Goodlatte (R-Va.) has since subpoenaed Simpson for a deposition.

Meadows and Jordan suggested Baker’s interview could be the most important for them as they prepare to speak with Rosenstein, to whom they plan to pose many of the same questions they asked of Baker about the FBI’s application to surveil Page.

Lawmakers also want to talk to Rosenstein about a New York Times report that he suggested recording Trump and potentially removing him from office. Rosenstein has denied he said those things, though he offered to resign in the wake of the report’s publication.

Baker is expected to return to Capitol Hill to finish his interview, which was cut short because of a scheduling conflict, Meadows and Jordan said. They described him as a “cooperative” witness.

Baker left the FBI in the spring, and now works at the Brookings Institution. He was a close associate of former FBI director James B. Comey, on at least one occasion receiving a memo Comey drafted following a meeting with Trump.

Baker was also linked to the members of Comey’s inner circle, including former FBI deputy director Andrew McCabe, who wrote memos detailing Rosenstein’s alleged suggestion of wiring the president; and former FBI counterintelligence official Peter Strzok and former FBI lawyer Lisa Page, who exchanged anti-Trump text messages. McCabe, Strzok and Page have left the bureau amid questions of their ethics and conduct.

Baker was caught up in a leak probe last year surrounding news reports about surveillance techniques of an email provider that appeared to stem from a dispute between the FBI and National Security Agency. He was accused by Republicans, in a report published by Politico, of disclosing information about the Trump-Russia dossier to Mother Jones, a left-leaning media outlet. David Corn, the author of that story, has denied that Baker was his source.

Baker was never charged with wrongdoing, but he was reassigned when FBI Director Christopher A. Wray took office. He left the bureau after a decades-long career this spring, and now works at the Brookings Institution think tank.