On the eve of the Iowa caucuses, Newt Gingrich lowered the boom on Mitt Romney in an interview with CNN’s Piers Morgan. Gingrich criticized his GOP rival as a “Massachusetts moderate” while touting himself as a “Southern conservative.” Asked if he ought to be responding more aggressively to attacks from Romney and the other Republican candidates, Gingrich said he would need to fight back, as some aides have reportedly been urging him to do.

“I would have been perfectly happy to run an entirely positive campaign,” Gingrich told Morgan. “[Romney’s] made that impossible.”