In the fall of 1998, testifying before the Judiciary Committee of the U.S. House of Representatives, Princeton historian Sean Wilentz prophesied that history would regard as "zealots" and "fanatics" members who sincerely believed they had good reason to vote to impeach President Clinton. In November 2000, days after the presidential election ended in stalemate, Wilentz assembled a bizarre group that included some of our nation's top professors of constitutional law (including Bruce Ackerman, Ronald Dworkin, and Cass Sunstein) mixed together with actors and other celebrities (including Robert De Niro, Rosie O'Donnell, and Bianca Jagger) and persuaded them to sign...