Well, the attacks aren't working. Between the fact that Rick Santorum isn't nearly as toxic to Republicans as Newt Gingrich and the fact that Romney damaged his own brand by going negative in Florida, Romney's playbook is in serious trouble, and conservatives aren't keeping quiet about it.
Today, National Review's editors accused Romney of "trying to win the nomination by pulverizing his rivals," adding that "his attacks on Santorum have been lame, perhaps because they are patently insincere." Richard Land, an evangelical conservative leader who hasn't endorsed a candidate, said Romney would be making a terrible mistake to go nuclear on Santorum. "Santorum’s a much more likable figure and a much harder figure to demonize than Newt Gingrich was," Land told Politico. "If he does that, there’ll be a backlash." And Byron York reports that late last week a group of conservatives at CPAC informed Romney that he should abandon his attack-dog strategy against Santorum.
All of that makes a fair bit of sense: Romney shouldn't expect beat Santorum by running his anti-Gingrich playbook from Florida. If he goes all-in on negative campaigning, he's likely to cause at least as much damage to his campaign as he is to Santorum's.
But as Adam Bonin points out, that still leaves Romney with a problem, given that the people who vote in Republican primaries and caucuses are, well, Republicans.
He can't attack Santorum for being too conservative and less electable -- which would be truthful -- and is stuck with lame attacks on Santorum's having actually served in the federal government. Other than that, Romney just has bio to run on.And between Bain Capital and RomneyCare, in the view of most Republicans, Mitt Romney doesn't have the most attractive bio to run on.