Party-related primacy effects in proportional representation systems: evidence from a natural experiment in Polish local elections

Abstract

We study the primacy effects that occur when voters cast their votes because a candidate or party is listed first on a ballot. In the elections that we analyzed, there are three potential types of such effects that might occur when voters vote for (1) the first candidate listed on the ballot in single-member district (SMD) elections (candidate primacy); (2) the first party listed on the ballot in open-list proportional representation (OLPR) elections (party primacy); or (3) the first candidate on a party list in OLPR elections (list primacy). We estimated the party primacy effect (2) and established that there was no interaction between (2) and (3). A party primacy effect is especially difficult to estimate because parties’ positions on ballots are typically fixed in all multi-member districts (MMDs) and it is impossible to separate the first-position “bonus” from a party’s normal electoral performance. A rare natural experiment allowed us to estimate the primacy party bonus between 6.02 and 8.52% of all votes cast for the 2014 Polish local elections. We attribute the large size of such bonus to the great complexity of voting in the OLPR elections, especially the much longer ballots, voting in many simultaneous elections, and ballot design as a booklet rather than a sheet.