In recent weeks, President Obama has chosen Sen. John Kerry, D-Mass., as his next secretary of state; former Sen. Chuck Hagel, R-Neb., to head the Pentagon; counterterrorism adviser John Brennan to be CIA director; and his chief of staff, Jack Lew, to be the next Treasury secretary.
Each nomination will have to be confirmed by the U.S. Senate, and they all could be stopped by a Senate filibuster — that is, the refusal by any one of 100 senators to let a matter come to a final vote.