For many practical purposes, it is the White House operations boss -- and not the vice president -- who serves as the nation's deputy president.
President Obama will soon make what could be the most important appointment of his second term: his chief of staff.
His choice will not have to be confirmed by the Senate or testify on Capitol Hill, and is not given nearly as much attention as controversial or high-visibility nominations to the Cabinet or to critical agencies, as is clearly the case right now with Defense (Chuck Hagel) and the CIA (John Brennan) -- or even Jack Lew, the current chief of staff and Obama's nominee for Treasury secretary.
But even though chiefs of staff often (though not always) try to operate out of the glare of the media spotlight -- and are often summarily described in the media as the West Wing "gatekeeper" -- given the fragmented nature of the federal government, the right chief of staff must effectively function as deputy president.
Watching what the White House chief of staff actually does is critical to an understanding of how the president leads. In the vast executive branch, only the chief of staff and the vice president have the same broad view of the total policy and political world as the president himself. But the chief of staff has a core operational role, while the vice president has, generally, had only a senior advisory one (with an occasional special project).