Mitt Romney isn’t the only one who heads into a debate with some zingers in his back pocket. Sen. Scott Brown and Elizabeth Warren faced off in their second senatorial debate Monday night, and things were just as nasty as the first time. Despite having to reprimand his staff for mocking Warren’s controversial claim of Native American roots with “tomahawk” gestures during a campaign rally last week, the Republican senator continued to push the issue of the opponent’s heritage. He also accused Warren of “misstating the facts” with regard to a number of jobs bills she said Brown and other Republicans had opposed. Warren began speaking over him and Brown declared, “I’m not a student in your classroom, please let me respond.” Zing.