From the NYT:
Mr. Huckabee’s renewed willingness to publicly criticize Mr. Romney follows a much-ridiculed reversal in the final days of the Republican caucus. After pledging to abstain from negative campaigning, Mr. Huckabee reversed himself and spent four days of tearing into Mr. Romney on the stump, then doubled back to renounce negative campaigning again.
He professed pangs of conscience and said he was pulling a prepared television commercial critical or Mr. Romney. But then he showed the attack commercial to a room full of news reporters at the same press conference, setting off an explosion of laughter at the apparent attempt to have it both ways. Iowa Republicans, however, appear to have applauded his efforts and rewarded him with their votes.