Polls show that Americans are confused about what health care reform means. And, if you listen to members of Congress on television, you get the impression that some of them aren’t certain, either. But figuring out what health care reform entails isn’t hard. All you have to do is look at Massachusetts.

Almost three years ago, the state introduced an ambitious initiative designed to make sure nearly all residents have health insurance. Under this scheme, the state requires employers to contribute toward the cost of covering workers, while requiring individuals to get insurance. It sets up regulated marketplaces, through which individuals and small businesses can obtain insurance, and it forbids insurers from denying coverage, or charging higher rates, because of preexisting...