Public interest groups may be defined as those groups pursuing goals the achievement of which ostensibly will provide benefits to the public at large, or at least to a broader population than the group's own membership. Thus, for example, if a public interest group concerned with air quality is successful in its various strategies and activities, the achieved benefit--cleaner air--is available to the public at large, not merely to the group's members. The competition of interest groups, each pursuing either its own good or its conception of the public good, has been an increasingly prominent feature of American politics in the latter half of the twentieth century.

There is no single, universally applicable definition or test of the public good, and thus there is often a great deal of disagreement about what happens to be in the public interest, with different public interest groups...