Organized interests are perennially under fire for distorting public policies. Critics charge that they privilege the demands of favored constituencies at the expense of the broader public interest. Yet despite the importance of interest groups in the political process, little systematic research has been conducted into the development of political identities and lobbying capacities among major advocacy organizations. How does a group come to represent a set of interests? Are the identities and policy priorities of advocacy organizations stable over time, or do they evolve? What causes such...