The paper presents the basic consequences of the introduction of single-member districts (FPTP system) in elections of municipal councils in Poland, bringing new evidence on the functioning of electoral rules in subnational elections, characterized by much more differentiated and open electoral markets. The authors compare the results of 2010 and 2014 local elections (before and after the electoral reform) in municipalities where previously used PR open-list system was replaced by FPTP and municipalities where no change was introduced. Basing on the difference-in-differences research scheme, the paper attempts to assess the impact of electoral reform on electoral supply, disproportionality and councils’ fragmentation. The analyses demonstrate that the introduction of FPTP system increased the number of committees competing in the elections. However, the disproportionality and share of wasted votes increased significantly, while the fragmentation of local councils decreased, resulting with more stable majorities supporting directly elected mayors.
