Duverger's Law

If anyone is following the discussion of my post below "The American Bipolarchy: Power Without Discipline," the question may arise: What is "Duverger's Law." Here is Wikipedia's explanation. On one level, it seems like a glorified way of saying "success breeds success" or, more relevantly, "failure breeds failure." Once a party establishes a record of finishing third or worse in legislative elections, Duverger contends, it faces an insurmountable obstacle to getting out of the rut. Again, this seems like stating the obvious, except that Duverger asserts that this is a condition peculiar to "single district plurality" elections, so that the way we vote supposedly influences whether we have a bipolarchy or not. This assertion has inspired people to argue that only voting systems that allow people to express multiple preferences, second choices, etc., can prevent bipolarchies from forming. Hence the appeal of "score voting," which I'll consider in a separate post. Duverger also asserts that ideology exacerbates the tendency of his Law, so that rightists, for instance, will consolidate into one big party to counter the influence of a strong leftist party, which in turn will draw all left elements into its embrace. This may be so, but I wonder whether any voting system can resist the pull of ideology more effectively. The hope is that multiple-preference systems would allow people to express very specific ideological preferences, but if the real problem is ideology itself, I'm not sure of the benefit of such a system. Nor do I see why Duverger's Law should apply automatically to every layer of a federal system like the U.S. Two particular parties may dominate the national scene, but that shouldn't automatically exclude independent parties (like Farmer-Labor in Minnesota back in the day) from playing a more powerful role at the state level. In any event, use the link to educate yourselves further about the concept, and don't feel left out of the discussion.