Countering the “Sweep Effect”

Abstract

One of the well-known properties of multimember plurality systems is their propensity toward producing the so-called “sweep effect,” manifesting itself in that the strongest party in a majority of districts sees its full slate of candidates elected even if the margin of plurality is small. Despite this property, and mostly for technical reasons, this system remains rather widely employed for conducting local elections both in democracies and in electoral authoritarian regimes. This article employs the evidence from the 2019 municipal elections in St. Petersburg to examine how increased strategic coordination of opposition voters became instrumental in countering the sweep effect and thus reducing the scope of political monopoly in an overtly authoritarian context. The analysis shows that this goal was achieved primarily by enabling opposition-minded voters to cast a greater number of votes than it otherwise would have been.