Still, Gingrich might know better than most this election cycle that negative ads work.
He has seen his support slide as the airwaves in Iowa have filled with ads reminding voters of his ethics woes, a public service announcement he shot with Democrat Nancy Pelosi and his lucrative work for Freddie Mac.
The libertarian-leaning Paul has assailed Gingrich for "serial hypocrisy," painting him as a career politician who lined his pockets after leaving office by selling access.
In an interview, Romney called him "zany."
How long can Gingrich keep up the positive façade? Asked if he would he would continue the commitment in a general election against Democrat Barack Obama, Gingrich dodged the question.
"Barack Obama's record is so terrible that if you just tell the truth it sounds negative," Gingrich said.