CEDAR RAPIDS, Iowa - December 9, 2011 - Newt Gingrich is ready to strike back at Mitt Romney.

Gingrich's campaign is holding a phone call Friday to have Iowa supporters attack Romney, the former Massachusetts governor. Romney's campaign started it Thursday, assailing Gingrich as irrational and unfit to lead, and Romney allies started airing a TV attack ad against Gingrich in Iowa. It's part of a $3.1 million campaign by Romney supporters.

Gingrich, the former House speaker, insisted Thursday he would stay positive.

But now his campaign goes on the offensive, using former Iowa Rep. Greg Ganske and Iowa state Rep. Linda Upmeyer to criticize Romney.