Geoffrey Cowan and presidential historian David Greenberg offered a behind-the-scenes look at the history and influence of the presidential campaign — from Theodore Roosevelt and the first presidential primary to today. Jeffrey Rosen, National Constitution Center president and CEO, moderated. Cowan is the author of Let the People Rule: Theodore Roosevelt and the Birth of the Presidential Primary. David Greenberg is the author of Republic of Spin: An Inside History of the American Presidency.