Chris Whipple, author of "The Gatekeepers: How the White House Chiefs of Staff Define Every Presidency," loosely describes the role of a White House chief of staff through his interview with former president Barack Obama: "During the last days of his presidency, Barack Obama observed: 'One of the things I've learned is that the big breakthroughs are typically the result of a lot of grunt work—just a whole lot of blocking and tackling.' Grunt work is what chiefs of staff do."