Replication data for: A Primary Cause of Partisanship? Nomination Systems and Legislator Ideology

Many theoretical and empirical accounts of representation argue that primary elections are a polarizing influence. Likewise, many reformers advocate opening party nominations to non-members as a way of increasing the number of moderate elected officials. Data and measurement constraints, however, have limited the range of empirical tests of this argument. We marry a unique new data set of state legislator ideal points to a detailed accounting of primary systems in the United States to gauge the effect of primary systems on polarization. We find that the openness of a primary election has little, if any, effect on the extremity of the politicians it produces.

诸多关于代议制的理论与经验研究均认为，初选（primary elections）具有极化效应。同理，诸多改革者主张开放政党提名程序，允许非党籍人士参与，以此增加温和派当选官员的数量。然而，受数据与测量条件的限制，针对这一论点的经验检验范围始终有限。本研究将一套独特的全新州议员理想点数据集，与美国初选制度的详细档案资料相结合，以此评估初选制度对政治极化的影响。研究结果表明，初选的开放程度对其所产生的政客的极端化程度几乎没有影响——即便存在影响，也微乎其微。