Mitt Romney stoutly defended his Massachusetts healthcare law in the face of its conservative critics, and called yesterday for replacing President Obama's national plan with a more state-based overhaul of the US healthcare system. In the first policy speech of his budding presidential campaign, Romney gave his strongest endorsement to date of the Massachusetts plan, including the decision to require residents to obtain health coverage. "A lot of pundits around the nation are saying that I should just stand up and say this whole thing was a mistake, that it was a boneheaded idea and I should just admit it,'' Romney said. "But there's only one problem with that: It wouldn't be honest. I, in fact, did what I believed was right for the people of my state.''