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Games, Diversions & Perl Culture by Jon Orwant

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Chapter 40. Pairwise Voting

Rob Lanphier

Editor’s note: This article was originally written in 1996, but still applies to current elections (unfortunately).

The U.S. Presidential election once again draws near, and once again we see a contest between two men, each representing one of the two major U.S. political parties. So it goes with the two-party system.

What is it that makes the two-party system a two-party system? It’s a direct consequence of plurality voting, the predominant form of balloting used in the United States where the highest vote getter wins an election. This relationship between the two-party duopoly and plurality voting is known as “Duverger’s Law,” after the 20th century political scientist who had the guts to call it a “law” (Riker, 1982).

Duverger’s Law has some disturbing consequences and leaves many voters dissatisfied with the status quo. Politicians will always claim to “feel our pain,” but at least in the U.S., two-party skeptics abound. Recent polls have shown that nearly 60% of Americans would support the formation of a new major party (Barrett, 1996).

The main reason Duverger’s Law rings so true is that we have a binary ballot that groups people into two categories: a winner and one or more losers. The resulting dilemmas that voters are faced with in siding with a winner manifest themselves several ways:

  • Because you can’t please all of the people all of the time, it is in politicians’ best interest to build divisions, and then build consensus among slightly ...

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