Mechanical Effects of Duverger’s Law in the United States

  • Michael P. McDonald
Part of the Studies in Public Choice book series (SIPC, volume 13)
Among the most enduring features of American politics is its two-party system. Since the emergence of contestation between the modern Democratic and Republican parties following the American Civil War in the mid-nineteenth century, these two major political parties have dominated elections to federal offices. The effective number of parties (Laakso and Taagepera 1979) in the US House rarely fluctuates far from a value of 2 (see Fig. 5.1). The exceptions are brief interludes where a handful of unaffiliated or minor party candidates win seats to the United States House of Representatives, such as immediately following the Civil War or during the heyday of Populist and Progressive parties near the beginning of the twentieth century. Indeed, deviations from two-party rule more often tend toward one-party dominance such as the overwhelming Democratic majority in 1890 followed by a stunning reversal by the Republicans in 1894, or the ascendancy of the Democratic Party during the Great...


Electoral System Vote Share Congressional Election Seat Share Major Political Party 
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© Springer Science+Business Media, LLC 2009

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  • Michael P. McDonald

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