Constituency Diversity and Party Competition: A County and State Level Analysis

Abstract

One of the staples of American politics is the theory that party competition is a function of constituency diversity. In Federalist #10 (see Rae and Taylor 1970: 7; Fiorina 1974: 89-119; Sullivan 1973) Madison emphasizes that increased constituency diversity facilitates factional dispute. As diversity increases, it weakens the ability of any single faction to represent the multifarious demands of people in a geographic area (The Federalist Papers 1961: 77-83). Despite this relatively simple and normatively pleasing explanatory perspective, and despite this theory’s broad acceptance in political science, the study of the relationship between constituency diversity and party competition has been one of the more elusive and sometimes contradictory research topics of the past 30 years. This article analyzes county level data from the 1970s and 1980s—the period that forms the basis of much of this literature—to assess the theoretical and empirical purchase of three of the dominant operational definitions for constituency diversity and then compares these county level findings with parallel state level analyses. I find that reformulated Lieberson/Sullivan social diversity indexes and Koetzle’s political diversity index produce similar results at the state and county levels of analysis. Moreover, these results are consistent with the theory that constituency diversity has a strong influence on the level of party competition.