The principle, often summarized, posits that a single-member district plurality election system favors a two-party system. Under such systems, voters are often strategic, selecting candidates with the highest likelihood of winning rather than their ideal choice. This strategic voting, coupled with the difficulty smaller parties face in gaining representation in a winner-take-all scenario, tends to consolidate political power within two dominant parties. A straightforward illustration is found in countries employing first-past-the-post electoral rules, where minor parties struggle to compete effectively with the established duopoly.
The significance of this principle lies in its explanatory power regarding the structure of party systems in different electoral environments. Understanding the connection between electoral rules and party systems allows for informed analysis of political stability, representation, and the potential for political change. Historically, the observation has provided a framework for interpreting the evolution of party systems and predicting the consequences of electoral reforms. This has implications for election design and understanding political outcomes.
