U.S. Attorney General Eric Holder faces a contempt vote by the House of Representatives on Thursday in a dispute involving a botched gun-running probe, and the chamber’s top Democrat, Nancy Pelosi, said some in her party may line up with Republicans against him.

The Republican-led House is to vote on whether to charge the nation’s top law enforcement officer with contempt of Congress related to his withholding of documents in a gun-running sting operation on the U.S.-Mexico border code named “Fast and Furious.”

The operation was run by the Bureau of Alcohol, Tobacco, Firearms and Explosives, which is part of the Justice Department that Holder heads.