Commentator, editor, teacher, public servant, best-selling author and adviser to presidents, David Gergen has been an active participant in American national life. He served as director of communications for President Ronald Reagan and also held positions in the Nixon, Ford and Clinton administrations. Gergen currently serves as editor-at-large at U.S. News & World Report and as a regular television commentator. He is also a professor of public service at Harvard's John F. Kennedy School of Government and director of its Center for Public Leadership. In 2000, he published the best-selling book "Eyewitness to Power: The Essence: of Leadership, Nixon to Clinton."