Legislative representation in a single-member versus multiple-member district system: The Arizona state legislature

Most research on legislative decisionmaking has focused on legislatures with single-member district systems, but much less is known about legislatures with multiple-member district systems. This study compares a multiple-member legislative chamber, the Arizona House of Representatives, to a single-member system, the Arizona Senate. First, we examine the ideological preferences across the two chambers, and we find that the House system produces more ideological extremism than the Senate. Second, we test a model of legislative decisionmaking that employs constituency variables, legislator attributes and ideology. We find that constituency characteristics are significant in the Senate, but in the House ideology dominates. The combination of ideological extremism and its greater importance in decisionmaking in the House suggests powerful effects of the multiple-member district system.