Very few presidential republics have sustainable third parties. Parliamentary republics, however, almost all have multiple sustainable parties. The U.S. and France are the only major democracies who have a separation of power between the legislature and the executive. The UK, Australia, Canada, Germany, Israel, Japan, and Korea are all parliamentary and have thriving multiple parties.

We will never see a third party in the U.S. because the Presidency represents only one party at a time. As a result, there is a high level of inertia pushing Congressional candidates to affiliate with the President’s party or with the opposition party.

Let’s say that one or a few Libertarians or Greens were elected to Congress. Even if they were able to convince a majority of their fellow Congressional Democrats and Republicans to support a piece of legislation, the President would veto it, assuming the legislation was not aligned with normal Republican or Democratic policies. Consider on the other hand that we had a parliamentary system with no President. Those newly elected third party members would wield real power.

I’m not advocating that we change our system, but for those clamoring for more parties, that would likely require us to fundamentally change our system of government to become a parliament. Or perhaps it could work with ranked-choice voting implemented in every state. There are plenty of people who would rather vote third party, but who end up voting D or R because they don’t want to waste their vote if their jurisdiction crowns the winner by plurality, rather than by majority or majority-runoff.