Long before the tea party movement became an American political phenomenon, Newt Gingrich chucked empty produce crates into the Chattahoochee River in Roswell as part of a tax day re-enactment of the Boston Tea Party. The year was 1994, and the Georgia congressman was months away from reaching the apex of his political career as U.S. House speaker. As he now seeks the presidency, Gingrich casts himself as an intellectual forefather of the grass-roots movement that has redefined Republican politics, and as the man best suited to harness its energy against the “establishment” choice, Mitt Romney. So far, tea party...