Structural Incentives for Political Party Polarization

Abstract

Politics is often thought of as a pie cut in half and split between republicans and democrats. A more accurate representation would be a pie cut into several uneven slices; most of the small pieces would go to the democrats and the few large slices would go to republicans. The existing literature on political parties indicates that parties are not mirror opposites of one another. Issue density is not uniform among the parties. Since the New Deal, democrats have pushed extensive policy from Social Security to new roads and dams. The trend to expand the scope of government policy continues today in the form of universal healthcare, combating global warming, and gay rights. The tendency of democrats to expand their policy agenda stems from the makeup of the party. Unlike republicans, the Democratic party is composed of a coalition of interest groups. Republicans, in contrast, can be described as ideological and have held consistent over time. Republicans are more easily thought of in terms of big ideological principles that include low taxes, defense, and family values. Republicans, being more ideological, have a few core tenants. Democrats, being a coalition of interest groups, have a wide and diverse set of principles but less support behind each issue area. Given two political parties, one with a smaller but deeper set of beliefs and a second with a wider and shallower set of beliefs, the group with a smaller number of principles will find it relatively more difficult to compromise. Since politicians are single-minded seekers of reelection, they try to capture a comfortable number of votes to become reelected; however, if the party with the smaller number of principles were to compromise on a single principle, they would risk losing a proportionally greater number of voters. For instance, let us assume two political parties ‘R’ and ‘D’. R holds two principles ‘1’ and ‘2’, while D holds principles ‘3’, ‘4’, ‘5’, ‘6’, and ‘7’. If R compromises on principle 2 to gain access to voters from principle area 3, they risk losing half of their voter base, assuming 1 and 2 contain equal numbers of voters who care deeply about that principle. Whereas if D compromises on principle 3 to gain access to voters from principle area 2 they risk only losing one-fifth of their voter base, assuming 3, 4, 5, 6, and 7 all contain equal numbers of voters who care deeply about that issue. Therefore, republicans are disincentivized from compromising while democrats have an incentive to work with republicans. Democrats compromise because they are likely to gain more votes from sacrificing small areas for a bigger traditionally republican area.