On domestic issues, Jonathan Cohn thinks the distinction is largely rhetorical:
Both have called for radical downsizing of government, with Santorum seeking to cap federal spending at 18 percent of gross domestic product and Romney seeking to cap it at 20 percent. Either cap, if enacted, would decimate key federal programs and all but certainly require undermining cherished social welfare programs like Medicare, Medicaid, and Social Security. Both want to repeal the Affordable Care Act, effectively taking health insurance away from 30 million people. Both have called for reducing taxes in ways that will disproportionately favor the wealthy. Both promise the deficit will come down – and both have sketched out fiscal plans that would, according to a recent report from the Committee on a Responsible Federal Budget, make the deficit go up.
The Dish 