Newt Gingrich, trying to reverse a slide in Iowa by positioning himself as the unabashedly positive alternative to his trash-talking rivals for the GOP presidential nomination, unleashed an unexpectedly harsh attack today against his chief rivals, former Massachusetts Gov. Mitt Romney and Rep. Ron Paul.

Gingrich has been the target of an avalanche of negative advertising, including TV spots, robocalls and brochures. He has often said in the last few days that he would take the high road. But his anger surfaced Tuesday when he was asked by CNN’s Wolf Blitzer what he would like to say to Romney about the attacks.

“All I’d say is, ‘Mitt, if you want to run a negative campaign and you want to attack people, at least be man enough to own it.’ ”

He said Romney was a “moderate Massachusetts governor, who is in fact very timid” with proposals for the economy.