Jared Cohen is the founder and CEO of Jigsaw and Alphabet Inc., who previously ran Google Ideas and served as a member of the Secretary of State's policy planning staff and as an advisor to Condoleezza Rice and Hillary Clinton. He is also the author of a new book on the presidency called, "Accidental Presidents: Eight Men Who Changed America." It describes the times in American history when a president has died in office, forcing eight other men, who are neither the voters' nor their party's choice, to confront unparalleled challenges. David Priess spoke with Jared recently about their stories and the lessons we can learn from their experiences.