HEALTH care reform is a case in point. Anyone who finds the Massachusetts health insurance mandate objectionable can easily move to live-free-or-die New Hampshire. A national mandate leaves people with fewer options. This is one way the health reform advanced by Mr. Romney as governor differs from that pursued by President Obama, and why the Massachusetts law raises fewer constitutional objections than does the national one.

While conservatives embrace governmental competition, liberals have good reason to worry about it. The left has a more expansive view of the role of public policy. Liberals want the government not only to provide public services but also to redistribute economic resources. In the words of President Obama, they want to “spread the wealth around.”

Yet redistribution is harder when people and capital are free to move to other jurisdictions that offer better deals. If you are going to take from Peter to pay Paul, Peter may well decide to leave. It is perhaps no surprise that state and local tax systems are less progressive than the federal one.

Whether competition among governments is good or bad comes down to the philosophical questions of what you want government to do and how much you fear government power.