The documents involved a botched U.S. gun-trafficking operation that was designed to track firearms headed into Mexico but which led to the disappearance of thousands of weapons, two of which were found at the scene of the 2010 shooting death of U.S. Border Patrol agent Brian Terry. The government has not ruled out the possibility that they were used in Terry's shooting.

House Speaker John Boehner said Terry's family deserved answers about the guns that killed him and went so far as to suggest a White House cover-up. Others specifically likened the actions of Obama and Holder to the Watergate scandal that brought down President Richard Nixon in 1974.

That may seem like a bit of a stretch, but in an election year outsized charges and countercharges tend to swirl.

Executive privilege has been claimed by presidents going back to George Washington to hide the inner workings of their administrations from congressional eyes.