Rich Lowry points it out well today:
The problem is that Huckabee so far appeals only to evangelical Christians (and there's no indication right now this will change). He's tried to broaden his appeal by running as a quasi-populist. It hasn't worked. Quote: "In Iowa, Huckabee played the religion card against his Mormon rival, all the while pretending he was doing no such thing. Then, he became enamored of his line that people should vote for a candidate who looks like someone they work with rather than someone who lays them off — another shot at Romney. He concluded his TV ad in Michigan with the line, but it got him nothing. Ordinary looks don’t constitute an economic policy. Huckabee’s campaign has been run on, to invoke two of his favorite substances, duct tape and WD-40. When reporters asked who his foreign-policy advisers were, he cited former ambassador to the U.N. John Bolton as someone with whom he has “spoken or will continue to speak.” But he never had. His advisers then said he had e-mailed Bolton, which he had once without ever following up. It was vintage Huckabee — slippery and laughably unserious."
Huckabee lacks substance, and in any case conservatives should always reject his form of bald populism--just as they rejected it 4 decades ago when George Wallace came calling.