DES MOINES, Iowa — If there’s one thing the Republican race in Iowa has proved yet again, it’s that negative ads work, no matter what voters say about wanting a nice, civil campaign.

When Newt Gingrich shot to the top of the polls in early December, a pro-Mitt Romney super political action committee promptly shot him down. Gingrich went from 25 percent in the last Des Moines Register poll to 12 percent in the new one. He might still be falling