The White House Chief of Staff is the highest-ranking member of the Executive Office of the President of the United States.
It can be a very powerful position, and the Chief of Staff is sometimes even dubbed "The Most Powerful Man in Washington." Some have even suggested that a powerful Chief of Staff dealing with a "hands off" president who decides not to become involved in the minutiŠ of government, can become a quasi-prime minister. Such prime ministers exist in some presidential systems, with the Prime Minister de facto running the system of government and the President standing back and setting broad policy agendas. James Baker and Donald Regan were seen as prime ministerial-style Chiefs of Staff during the Reagan presidency. Howard Baker, who succeeded Regan, was critical of this system and what is sometimes called the Imperial Presidency.
By contrast, Andrew Card, the Chief of Staff within the administration of George W. Bush is not regarded as a very powerful figure, in large part because Bush appears to deal directly with his Cabinet secretaries.
The duties of the Chief of Staff can vary greatly from administration to administration, but generally the Chief of Staff is responsible for overseeing the actions of other members of White House staff, managing the president's timetable, and controlling outsiders' access to the president. This last duty has often earned the Chief of Staff the nickname of the "Gatekeeper."
Informally, the Chief of Staff is often one of the President's closest political advisors, and a close friend.
Not every President has had a formal Chief of Staff. Presidents Kennedy and Johnson never did, nor did President Carter until the very end of his term.
Most Chiefs of Staff are former politicians, and many have gone on to successful post-Chief of Staff political careers. Notable mentions include Richard Nixon's Chief of Staff Alexander Haig who later became Secretary of State, Gerald Ford's Chiefs of Staff Dick Cheney, now Vice President, and Donald Rumsfeld, who later became Secretary of Defense.
White House Chiefs of Staff: