Duverger's Law and the One-Party State

A post at Stand Up for America considers the prospects for the emergence of a viable third party in the current political climate from the national to the local level and concludes, "Americans are disenchanted with the two big parties, and that means there is an opportunity." Along the way, he notes that one of the reasons why the US two-party system has proven so impervious to third party agitation is because single-member district plurality voting tends to favor a two-party system (i.e. Duverger's Law).

Duverger's Law is often referenced by partisans of the duopoly when dismissing third party activism in favor of the status quo, and consider the case a settled matter. Yet things are not as simple as the realists would have us believe. Let's note first that Duverger's Law is no more a law than the Federal Reserve is federal, to paraphrase Dennis Kucinich. There are numerous exceptions to the French sociologist's rule of thumb: Canada, the United Kingdom, Scotland, India, and even Vermont, where the Progressive Party has made inroads into local and state government. More importantly, however, as applied in the US context, the 'law' states that SMDP voting favors a two-party system, not the Republican and Democratic Parties. Of course, in the US, 'the two-party system' effectively means the Republican and Democratic Parties, but the point is that the parties in their particularity are immaterial to the law.

In other words, even though SMDP voting tends to reduce a given district's system to a duopoly, it does not favor a particular duopoly constellation. The latter is rather determined by other outside factors (money, historical inertia, name recognition, the dispositions of voters etc.). It is thus not impossible - and may even be likely under the right conditions - that districts with radically lopsided majorities in favor of one or the other reigning duopoly parties will witness the other devolve into a third party, fighting for second place with a party more in tune with the given electorate's sensibilities. According to Duverger's Law, SMDP favors a two-party system, not a one-party system.