The spy agency’s resistance comes amid intelligence officials’ deep skepticism of the probe, which is being led by Sen. Ron Johnson (R-Wis.) and focuses on Hunter Biden’s role on the board of the Ukrainian energy company Burisma. Democrats argue the investigation is based on Russian disinformation aimed at tipping the outcome of the election toward President Donald Trump — a charge Johnson rejects.

Some intelligence officials similarly fear the Biden probe will only boost the Russian intervention. And while the motivations of the CIA are not certain, Johnson is considered “toxic” by some members of the intelligence community, according to people with direct knowledge of the dynamic.

The agency’s reluctance to engage with the Senate Homeland Security and Governmental Affairs Committee, which Johnson chairs, underscores the intelligence community’s doubts about the probe. And while it is unlikely to deter Johnson from moving forward, it could give Democrats more support as they seek to rebut Trump and GOP allegations that Biden is corrupt.