Peyton Cabot Harrison III was a judge who was to be nominated by President Bartlet to the United States Supreme Court (episode: The Short List). Harrison was educated at Philips Exeter Academy and Princeton University and was Editor of the Harvard Law Review. He also served as Dean at Harvard Law School. His father served as Attorney General for President Dwight Eisenhower. A lifelong Democrat, he clerked for Warren Burger, and never wrote an opinion on abortion.
After Sam Seaborn receives a phone call from an unnamed source, it is determined that Harrison was the author of an unsigned note thirty years earlier on right to privacy, which he asserted the Constitution does not guarantee.
The President, Toby, and Sam question Harrison and decide to meet with Mendoza. Once Harrison is no longer an option, President Bartlet nominates Judge Roberto Mendoza.
He was a member at Sandy Hook, a golf club where Charlie once worked.
Peyton Cabot Harrison III was played by Ken Howard.