With both major political parties having significantly net unfavorable rating it is no surprise that Americans desire increased diversity in our political choices. 46% of Americans agree the country needs a third party to compete with the Democrats and Republicans. Given the level of dissatisfaction with the status quo, one might wonder why we are stuck with basically only two choices in our elections. It’s not for a lack of desire for alternative choices, nor is it that our society is inherently an evenly divided country which naturally creates a two-party system. It’s our electoral laws which have evenly divided us.

Our politics are defined by mainly single position election with plurality voting (or first past the post). Whether voting for governor, senator, congress, president, etc., our elections can produce only one winner and the winner is whoever gets a plurality of votes. This inherently discourages political parties that may have significantly less support than the two dominant parties — say 25% of voters. Since they can rarely gain a plurality in any one election they can’t secure many elected positions. In other systems which use proportional representation this is not the case. A party with 25% of the vote would often end up with around 25% of the seats in the legislature.

What this kind of election system produces is a spoiler effect. Picture a single position winner-takes- all election with two legitimate right-leaning candidates and only one left-leaning candidate or vice versa. Even with a very conservative electorate the left-leaning candidate could easily win with a very small plurality. A divide center-right hands victory to united left-leaning choice and a divided center-left will hand victory to a united right-wing choice. Hawaii’s 1st Congressional District special election offers an example of this dynamic at work, where a Republican could win an overwhelmingly Democratic district with just over a third of the vote due to a divided left. Without proportional representation, instant run-off voting, or even very quick run-off elections, voters would constantly run up against the spoiler effect, inhibiting the emergence of new parties.

The current election cycle in the United Kingdom provides an interesting case. The traditional third-party Liberal Democrats are surging because of much unhappiness with the two major parties, Labour and Conservatives. But since they use a similar system of single member districts with plurality winners, the Liberal Democrats could get more votes nationwide than either the Labour or Conservative parties but still end up with few seats in parliament than both.

Compounding our American challenge, we have a national election for the presidency. Without this particular election in its current format, we could see the emergence of regional parties (for example Bloc Quebecois in Canada), or third parties that compete in the few districts which are much more conservative/liberal than average. But having a national presidential election produces the spoiler effect nationwide. We are driven further into a two-party paradigm since third parties could not run viable president candidates; in our system the president is generally viewed as a leader of their respective political party.

The U.S. is not an inherently divided country split between two ideologies. Nor do American voters actually want a two-party system; they don’t believe this offers a sufficient set of choices. This dichotomy is a result of our election system’s structure and will not change until our election laws are changed. It also means that we are doomed to experience zero sum political campaigns and policy fights, because the system prevents the emergence of third parties that could equally punish Republicans and Democrats when they both behave in a way that disappoints the electorate.

Instead the two parties will continue to see value in trying to tear each other down. In a two-party zero sum political system it does not matter how far you lower your own standing as long as you bring the other party down even farther. If Americans want more choices and less zero sum politics they will need to push for changes to election laws which make this possible.