This week on "Face the Nation," host John Dickerson sits down with Robert Dallek, author of "Franklin D. Roosevelt: A Political Life," Ron Chernow, author of "Grant," Nancy Koehn, author of "Forged in Crisis," and Mark Updegrove, author of "The Last Republicans" for a discussion about their works which examine leadership in times of crisis. Plus, Walter Isaacson discusses his new book "Leonardo da Vinci" which explores the life and work of the original renaissance man.