But why must this be the debate? Surely, in some alternate universe, lesser U.S. parties could influence the election significantly. So let’s ask a different question: Do third-party candidates have a chance in 2016?
Political science says no.
Why? The answer lies in what is known among political scientists as Duverger’s Law.
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Here’s how it works. First, when each district gets only one legislative seat (known as a single-member district, which we have in the United States) and, second, when the election’s winner takes that seat, then the system tends to have two dominant parties.
In such a system, all a party needs to win is more votes than the other side. That winner-takes-all nature of single-member districts encourages broad coalitions to form before elections. The odds of a party winning such elections are much higher if only two parties exist, enabling each side to work to bring as many people to its side as possible.
In the United States, that’s writ large in presidential races, because the Electoral College is itself a winner-take-all system: Within each state, the candidate who wins more votes takes all that state’s electoral votes. Even in Nebraska and Maine, where electoral votes are allocated by congressional districts, each individual district is winner-take-all.
So what’s the alternative? In many countries, each district gets many seats, and they are allocated in a way that proportionally matches the votes each party receives. In those systems, there will be many parties. That’s because a party has a much lower threshold for gaining a voice in government.
