By Ethan Hollander, Wabash College
When it comes to the number of political parties, Germany has five or six, and places like the Netherlands or Israel have dozens—each with a realistic shot of winning parliamentary seats and serving in a ruling coalition. So then, why does the United States have just two dominant political parties? Are two-party dominant systems better?
Coalition Politics
In a place like the United States, where there’s a single (and very powerful) president, most people don’t want to vote for a third party—even if they like what it stands for—because there’s only going to be one president, and voting for a third-party candidate can feel like throwing away a vote.
But if there’s a realistic chance of coalition politics—of a prime minister building a coalition of a few political parties—and, in that case, the situation is a little different. Now, voting for a minor party isn’t throwing away our vote, because a small party—even if it can’t win the prime ministership—can still play a meaningful role in the governing coalition. This is just one of the reasons why one is more likely to see multiparty politics in parliamentary political systems, and two-party politics in presidential systems.
Competitive Political Parties
A similar thing happens at the local level. And this can be another reason why some systems have a tendency to see the development of just two competitive political parties, rather than many.
In the United States and in the United Kingdom (and in a handful of other countries), we generally have one parliamentary or one congressional representative per district. Everyone in the United States has only one representative in the House of Representatives. (Unless one lives in Washington DC, in which case they have zero!)
But one could imagine a system where each legislative district had, say, two or three representatives, or even more, all of whom run for office at the same time. And it turns out that having multiple representatives per district also tends to enhance the number of competitive political parties.
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Duverger’s Law
Let’s say there was a legislature with 200 members, but only 100 districts, with each district electing two representatives. (We call these multimember districts, rather than single-member districts.) Notice how, in that case, voters no longer feel penalized for voting for third parties. One’s third-party vote might be enough to put their preferred candidate in second place (rather than third)—and in a two-member district, that would be enough for that person to win a seat.
So, in comparative politics, we see a clear trend, first discovered by the late political scientist, Maurice Duverger—and therefore, it’s called Duverger’s law. And this trend suggests that single-member districts will usually give rise to the creation of just two dominant political parties, whereas when the number of representatives per district goes up, so too does the number of competitive political parties.
For good or for ill, the use of single-member districts is yet another reason why the US and the UK seem stuck with their two-party dominant systems.
Multiparty Democracies
In fact, there are political systems where voters vote for political parties rather than individual candidates. And these voting systems also tend to increase the number of political parties, sometimes quite dramatically.
These are called party-list election systems, and they’re used in a lot of the world’s multiparty democracies: Italy, Spain, Portugal, Israel, and a host of newer democracies in Eastern Europe (Poland, Romania, Bulgaria, and so on). And they use a close variant of this system in the Netherlands, Switzerland, and Scandinavia.
Proportional
Party-list voting systems are perfectly proportional. Voters vote for a party, not a person—and then, whatever percentage of the votes the party gets, that’s how many seats the party gets in the legislature.
This kind of radical proportionality has a tremendous effect on the party system, and thus on the character of democracy more generally. Think about it. A political party that gets just 6% of the vote, well, in a list system, will now get about 6% of the seats. This wouldn’t be enough to win the top job, like the prime ministership, but it might be enough to get a place in the ruling coalition. (Contrast this with a single-winner district, where a tiny political party probably wouldn’t win anything at all.)
Focused on a Narrow Set of Issues
Moreover, these political parties aren’t just small; they’re often specialized and focused on a narrow set of issues. Let’s face it, if one only has to win a few percentage points to get seats in parliament, they can afford to cater to a pretty narrow slice of the electorate.
But despite their small size and narrow focus, minor political parties can wield tremendous influence.
Take a case of the Netherlands, which uses a variant of the party-list system, and which consistently has a dozen or so political parties in its House of Representatives. And to give a sense for how narrowly tailored these parties can be, there’s an animal rights party, in addition to two green parties, and there’s a 50Plus Party, which advocates for pensioners and retirees.
Having Disproportionate Influence
While some of these parties only have a few seats each, there are so many political parties—and the votes are so spread out—that even the major parties only have 20% or 30% of the seats.
This means that the bigger political parties need the smaller ones in order to get a majority, and to get anything done. In the Netherlands, one is usually not going to be able to form a government, or to pass laws, without a handful of parties in their coalition—whatever is necessary to get past the 50% mark. Hence, in a multiparty democracy, tiny political parties can have disproportionate influence.
Common Questions about Two-party Dominant Systems
This is because a small party—even if it can’t win the prime ministership—can still play a meaningful role in the governing coalition.
The Duverger’s law suggests that single-member districts will usually give rise to the creation of just two dominant political parties, whereas when the number of representatives per district goes up, so too does the number of competitive political parties.
Party-list voting systems are perfectly proportional. Voters vote for a party, not a person—and then, whatever percentage of the votes the party gets, that’s how many seats the party gets in the legislature.
