One of Romney’s weak arguments was that the Massachusetts plan was fundamentally different, as a matter of policy, because it had been enacted on a state rather than federal level. The argument got little traction and Romney, after an effort in the Spring of 2010 to explain his record, simply fell silent.

Romney’s argument is now much stronger. Because the main objection to ObamaCare, as its critics call it, is no longer a matter of policy nuance. Now critics primarily make the case that it’s an unconstitutional expansion of specifically federal power. And on that turf, the similar structure of the plans doesn’t matter. Romney enacted his at a state level, and states have — conservatives argue — more power to regulate the insurance industry, as they do with car insurance.