Bill Clinton's days in the White House are nearly over. As the first democrat to win two terms since Franklin Roosevelt, Clinton has been called the best politician of his generation, yet he is also the first elected president in the country's history to be impeached, and he leaves behind a polarized political landscape and a trail of disappointed friends and former supporters.

David Gergen, author of Eyewitness to Power: The Essence of Leadership, Nixon to Clinton, used to work for President Clinton. But that's just a small part of an impressive résumé—he also worked for Presidents Nixon, Ford ,and Reagan. Gergen writes about his experience and the leadership styles of each of those four presidents in his new book.

Gergen is also well known as regular contributor to the NewsHour with Jim Lehrer on public television and ABC's Nightline. He's also Editor at Large with U.S. News and World Report and Professor of Public Service at the John F. Kennedy School of Government at Harvard University