Nick Gillespie and Matt Welch point out that duopolies rarely endure because they tend to abuse their customers. That creates an opening for competitors to enter the market.
Political markets are different than economic ones, but duopolies still have many of the same qualities -- particularly regarding customer abuse. That's why I was pleased to see a writeup in this morning's Politico that the percentage of political independents is at an all-time high in a long-running Gallup poll. A full 40 percent of Americans have now opted out of the Republican-Democrat duopoly.