Represented by or Within Parties? How Electoral Systems Shape Party Factionalism

While majoritarian electoral systems tend to reduce the number of parties in a polity, they do not necessarily reduce the ideological heterogeneity of the electorate and the diversity of interest groups to be represented. This creates a dilemma for the representation of the electorate since few but large parties might not be able to aggregate too heterogeneous interests. This paper argues that when there is no space for more competitors in the party arena, this dilemma is solved through party factionalism. Specifically, factions representing different ideological viewpoints within parties serve under majoritarian electoral systems as functional equivalent to political parties under proportional electoral systems. Using a novel data set on party factions assembled through expert interviews with political journalists in 8 countries, the argument is tested with a QCA-analysis. I find indeed that ideological factions are more likely to emerge under disproportional electoral systems, but also surprisingly that societal interest groups representing women, employees or ethnic minorities are more likely to emerge under proportional electoral systems. The findings indicate that parties can also represent under majoritarian electoral systems the ideological diversity of the electorate through factionalism, but that parties have a representation premium under proportional electoral systems since ideological heterogeneity is represented by and the diversity of societal interest groups within parties. These findings have important implications for political representation since the advantage of proportional over majoritarian electoral systems appears to be rather in the descriptive representation of societal groups than the substantive representation of ideological differences.