Ideological extremism and electoral design. Multimember versus single member districts

Relying on a formal theoretical model, Gary Cox demonstrates that single member districts induce candidates toward policy positions at their constituency median while multimember districts encourage dispersion. We test this theoretical implication in the context of the Arizona state legislature, in which each legislative district chooses one senator and two representatives in single member and multimember contests respectively. To do so, we generate W-NOMINATE estimates of scores based on roll-call data from the Arizona state legislature that are comparable across chambers (Senate and House). Our results are substantially less supportive of the formal theory than are those of prior studies.