House Republicans and some conservative Democrats are poised to hold Attorney General Eric Holder in contempt of Congress on Thursday for withholding documents in the investigation into botched Operation Fast and Furious, which let guns slip into the hands of drug cartels.

House Speaker John Boehner is pressing ahead with a floor vote that is almost certain to pass, with the majority Republicans expected to get the backing of some Democrats. At least five Democrats so far have said they plan to vote to hold Holder in contempt, and sources tell Fox News as many as 11 appear ready to break ranks.

Those Democrats are largely conservative-leaning lawmakers facing perilous political circumstances in their home districts. But regardless of motive, their support only increases the odds that the nation's top law enforcement official will be held in contempt of Congress come Thursday.

The vote against