Academic journal article Political Research Quarterly

Falling into a Niche: Institutional Equilibrium between Plurality and Proportional Representation for Large Political Parties

Academic journal article Political Research Quarterly

Falling into a Niche: Institutional Equilibrium between Plurality and Proportional Representation for Large Political Parties

Article excerpt

Scholars of electoral systems (e.g., Duverger 1954; Rae 1967) argue that a combination of electoral system and district magnitude provides the strategic incentives for political party competition. All electoral systems reward large parties with a disproportional seat bonus, with this bonus being more pronounced in plurality/majority systems. Thus, large parties invariably wish to compete in majoritarian systems while smaller parties seek a proportional system of seat allocation. This study shows that an institutional "niche" develops in some party systems where the second-largest party prefers the current electoral system over either a more proportional or more majoritarian system. Specifically, I illustrate how parties in Irish, Tasmanian, Australian House, and Australian Senate elections occupy such an equilibrium. Vote transfers create a seat bonus that does not exist in either more proportional or more majoritarian systems (e.g., the Single Non-Transferable Vote).

Since the work of Maurice Duverger (1954), one of the most fundamental ideas in political science is that a party system is shaped by the electoral institution that it possesses. The particular effects of each electoral system can be systematically derived and predictions made of the normative consequences. Duverger states in his famous Law that plurality electoral systems favor twoparty systems while systems of Proportional Representation (PR) are associated with multiparty systems. While the deterministic nature of this relationship between electoral system and party system is debatable, it is generally accepted (Riker 1976,1982,1986; Sartori 1976,1986; Taagepera and Shugart 1989; Lijphart 1994).

Perhaps the most fruitful and encompassing work in a similar vein is that of Douglas Rae (1967). He makes bold observations about not only the properties of each electoral system (his "similarity propositions"), but also about the comparisons between different electoral systems (his "differential propositions"). Rae finds that in all electoral systems there exists "a relative advantage of strong elective parties over weak ones" (Similarity Proposition One). Rae defines a "large" (i.e., "strong elective") party as any party with greater than 20 percent of the vote and that all systems slightly favor the top two vote-getting parties (hereafter referred to as "large parties").

By Rae's definition of a "large" party, Similarity Proposition One usually pertains to not only the largest party, but to the second largest party as well. Both parties, individually and collectively, benefit from their size. The political significance of this overrepresentation is the "manufacturing" of majorities (i.e., a party obtaining a majority of seats without a majority of votes) (Similarity Proposition Three).

Rae determines that the large party seat bonus is more pronounced in plurality/majority electoral systems than in proportional electoral systems (Differential Proposition One). He also illustrates the role that district magnitude (i.e., the number of seats awarded in the district) plays, stating that a positive relationship exists between district magnitude and proportionality (Differential Proposition Ten). Thus, there should be a positive incentive for large parties to desire more majoritarian systems, while the smaller parties should prefer more proportional systems.

Other work has confirmed and extended Rae's findings. Sartori (1976) emphasizes Rae's predicted correlation between proportionality and district magnitude. The logic of his argument is that a small district magnitude allows only a small number of parties to gain effective representation, while a larger district magnitude allows a greater number of parties to win seats. Sartori (1976,1986) posits that all electoral systems possess incentives for strategic voting. The more proportional the electoral system, the fewer incentives exist. Therefore, as the district magnitude increases, proportionality and the number of parties increase. …

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