Does IRV entrench the “duopoly” two-party system?
No more than any other single-winner election method. Some opponents of the American “two-party system” have suggested that IRV would simply entrench what they call “duopoly.” IRV neither over-throws, nor entrenches the current domination of two major parties. IRV does allow minor parties to exist, contend for office, and possibly eventually supplant one of the existing major parties without being labeled as “spoilers.” However, since IRV is a majority voting method, third parties that do not appeal to the majority of an electorate would not generally win. Only a proportional representation voting method (which IRV is not) is likely to result in the election of substantial number of candidates from more than two parties. Like every non-proportional, winner-take-all voting method (including plurality, approval, range, condorcet, borda, etc.) “Duverger’s law” suggests two parties will tend to predominate in such winner-take-all electoral environments.
