Recent events leading to the importation of democratic ideas and ideals by previously totalitarian states increase our interest in the ways in which electoral institutions influence party systems. However, even if we restrict our attention to Eastern Europe or the successor states of the Soviet empire, we encounter a range of social diversity – ethnic heterogeneity - that is as great as those in the set of countries examined in earlier studies that seek to identify the influence of electoral laws (c.f., Rae, Lijphart, and Taagepera and Shugart). Curiously, though, these earlier studies fail to ascertain whether and to what extent electoral laws mediate the influence of this heterogeneity. Hence, to develop a more pragmatic understanding of electoral institutions, we adopt the view of electoral laws as intervening structures and, using the data of these earlier analyses, we reconsider the role of one institutional parameter - district magnitude - that some researchers regard as the most important characteristic of an electoral system. Aside from the usual caveats about the limitations of our data, our primary conclusion is that district magnitude is not merely an important determinant of the number of parties that compete in a political system, but that it can offset the tendency of parties to multiply in heterogeneous societies
