For those who have not been continuously insured, Mr. Romney favors risk pools. This is a cheaper and less destructive solution to the problem of pre-existing conditions. But here the danger is that risk pools must be structured judiciously, lest they also encourage the healthy to remain uninsured.

There is an even better idea: to insure yourself against the possibility of becoming uninsurable, as suggested by economists including the University of Chicago’s John Cochrane on this page in April. Under this approach, policies would be guaranteed to be renewable and include the right to buy another policy in the future. If your health condition worsens, a new insurer would be free to charge you a higher premium. But the old insurer would pay the extra premium caused by the change in your health status.