American politics is dominated by two major parties and has been for a century. The duopoly enjoyed by the Democrats and Republicans is largely the result of Duverger's Law: the tendency of a single-member district system to produce two-party competition (Duverger 1963). Minor parties ultimately fail in a single-member district system because (1) the winner-take-all approach does not reward candidates who finish third and (2) citizens vote strategically to avoid “wasting” their votes on hopeless candidates and spoiling the election (Cox 1997; Riker 1982). Because the U.S. two-party system is so dependent on its majoritarian electoral rules, one might suspect that other election regulations would have little effect on the number of parties.
Email your librarian or administrator to recommend adding this journal to your organisation's collection.