Eli5: Duverger’s Law

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I keep reading the definition but i still cant seen to understand any help please?

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4 Answers

Anonymous 0 Comments

In political systems where there can be only 1 winner of an election, 2 parties emerge that dominate the system. Usually one more right-wing and one more left-wing.

Because of the lack of real choice people end up not voting for the party they want, but rather against the party they hate.

Since only 1 of those 2 parties has any real chance of winning, other minor parties become effectively politically irrelevant and ultimately only take away votes from the larger parties when they become unpopular.

This effect isn’t nearly enough to get the minor parties elected, but it is enough to prevent the major party from losing.

In the US they call this ‘the two party system’

Anonymous 0 Comments

If only 1 person can win an election, you will eventually end up with 2 bad choices with people voting against the one they dont like rather than for the one they do like.

Anonymous 0 Comments

Ahh ok i have a better understanding now thanks plenty

Anonymous 0 Comments

I feel like some of the other answers are incomplete.

The core of Duverger’s law is that certain election systems, by the very rules of the game, tend to create systems with two strong parties, and if any third parties exist, they are small and weak. The specific systems that cause this effect are single constituency, plurality-wins systems (sometimes called first-past-the-post systems). Broken down:

* Single constituency: There is only one position (usually called a seat) available per election district. For example, you can’t have more than one President of the United States. This doesn’t mean you can’t have more than one election simultaneously–so you can vote for the President, a Senator, and a Representative at the same time–but you can’t have two different Representatives for the 50th Congressional District. This naturally means that winner-takes-all; other parties get no say in what the winners do.
* Purality-wins: Whoever gets the most votes, wins. You don’t need a majority of votes (50% of votes cast +1 vote) and you don’t need a majority of citizens. Just more votes than any other candidate.

In a system like this, it’s hard to get a small party started because you need more votes than any other candidate in a particular district to win; you can’t start small and get bigger, because you need to be big in the first place just to get elected, and if you don’t get elected, nobody will take you seriously, and you will have no influence on the process of government, which means it will be hard to draw any new votes.

There’s also the issue that both the existing big parties, and the voters themselves, have an incentive to prevent small parties from starting or succeeding. This is sometimes called the “spoiler” effect: If there are three parties, the two which are ideologically the closest to each other will “steal” votes from each other and hand victory to the other party. This has happened several times in US history, for example. Theodore Roosevelt formed the Bull Moose Party to run for a third term in 1912 because he didn’t like the President that the mainstream Republican party had gotten elected to succeed him, William Howard Taft; but this effectively split the Republican vote and allowed Democrat Woodrow Wilson to win the election.

Another way to illustrate the law is to look at what happens under other kinds of electoral systems, particularly parliamentary proportional representation systems as frequently seen in Europe. Under a proportional representation system, voters don’t vote for candidates, they vote for parties. When the vote is counted, each party gets a number of seats in the legislature corresponding to the percentage of the votes that they won; sometimes they then pick who gets to fill each seat, sometimes they have to release a slate of candidates beforehand.

In any event, in order to actually make laws and govern, they need a 50%+1 seat majority in the parliament. If one party is so popular it got 51%, all well and good, they win entirely, and can do whatever they want. But since it’s possible to win say, 5 seats with 10% of the vote, a small party can get representation even without a plurality; and if the big party can only get, say, 41% of the vote, then it will need to compromise with at least 10% of the other representatives to actually do anything. That small party now has real power because it can either enable or obstruct the bigger parties.

Thus: single winner plurality systems create two-party systems by their very nature. When people complain about the two-party system in the US, they’re complaining about the electoral system. The only way to change it would be to amend the constitution.