Externalities, Social Pressures, and Political Parties

Members of political parties talk to each other often, and may thereby influence each other. For example, a liberal in a party of moderates may moderate his views. At the same time, the moderates in the party may become more sympathetic to liberal views. Voters in a district may favor such effects if they care about the ideology of officeholders in other districts. They may therefore prefer a candidate who affiliates with a party over an independent with the same position.