Our research finds more links between partisanship and U.S. rules

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August 8, 2018
Kevin Johnson

Research ERN conducted this week provides further evidence for the core argument of Election Reformers Network: that our rules themselves are a source of political dysfunction and partisanship.Political scientists measure partisanship with a tool called the NOMINATE score, which ranks elected representatives based on their roll call votes (with +1 being extremely conservative, and -1 extremely liberal). Whether a given districts representative has an extreme or moderate score is mainly determined by political factors such as the demographics of the district. But we believe the mechanics of our elections also play a role, in particular the mechanics of primary elections and whether primaries are won with a majority, or with a small plurality in a crowded field. This theory directly relates to the election reform weve committed to first, Ranked Choice Voting, which is well designed to identify the majority-supported candidate in a crowded election.To test our idea, we compared members of the 115th U.S. House of Representatives on the basis of their NOMINATE scores, taking into consideration the primary election results when the members first won seats in Congress (before the power of incumbency weighs in). The table below shows initial support for our hypothesis that low plurality primary winners tend to be more ideologically Right or Left in Congress.

To address the possibility that this analysis could be skewed by more partisan districts inherently generating more crowded primaries, we used Cook Partisan Voter Index data to control for district. We calculated an expected nominate score for each Congressional district and then measured members on the difference between the actual and expected scores. This approach shows an even clearer pattern: members who entered Congress with a low plurality primary victory were significantly more partisan relative to their districts than those who won majority support.

This issue is significant in scale and growing in intensity. We were surprised to find in this research that less than half the members of the 115th House (213 out of 435) won their first primary with a majority. 80 representatives had 35% support in the primary or less (a figure that does not include California and Washington, because of their top-two open primary systems).As grassroots political organizations strengthen, parties are losing control of the candidate nomination process. As a result, primaries become more crowded, particularly for open seats, and more plurality winners enter Congress. It isn't automatic that every low plurality winner will be a more ideologically extreme legislator, but on average more low plurality winners are likely to make Congress more extreme, to the Left and the Right, than the overall population. This year at least 146 U.S. House primaries will have five or more candidates, more than double the total for any recent election (see chart below). 212 primaries will have four or more candidates.

The solution to this problem is ranked choice voting, which allows voters to support multiple candidates in order of preference and nearly always results in a winning candidate who has support of the majority.  In the past, ranked choice voting has been something of a nice to have for more liberal cities, like Cambridge Massachusetts. In an atmosphere of increasing political extremism, and in the context of much more crowded elections, ranked choice voting is now a need to have.