It should be noted that the founders did not explicitly include political parties in the Constitution. George Washington, in his farewell address, actually took timeout to warn citizens of the “baneful effects of the spirits of party”. Still, parties formed, and it is difficult to imagine a functioning democratic system that does not have political parties. This is because parties actually do serve some very valuable functions. Perhaps most importantly, political parties reduce the cost of gathering information (in time and energy, not just money) so that we can actually participate without having to immerse ourselves in politics every moment of every day. Parties serve as organizing forces that simplify the information required to make an “informed” voting decision. For example, if you know that Mrs. X is a Republican, you don’t have to do much additional research to know her views on abortion, taxes, the death penalty, government regulations, etc. This allows us as citizens to engage/participate politically with only minimal time spent gathering information on the candidates. Without parties, you would have to research each candidate’s views on each issue that matters to you, leaving less time and energy for commerce, family, or your own personal interests.
For the sake of continuing the discussion, let’s assume parties do indeed serve a central purpose in our system. Now to address the system itself. The U.S. has what is called a Single-Member-Plurality-District (SMPD) system for electing representatives to Congress. What this means is that in each district, there is only one winner. The candidate that gets more votes than any other candidate in that district wins (this is referred to as plurality, or first-past-the-post…a majority of votes is not required). There is no prize for second or third place, it is “winner-take-all”. So, if your preferred candidate is polling at 10% while the other candidates are polling at around 45% each, what are you going to do with your vote? You basically have few options. You can vote for your candidate that has no chance of winning (a symbolic vote), or you can determine which of the remaining candidates most closely represents your interests, and vote to insure that candidate beats the competitor that least represents your interests. This is referred to as strategic voting, though on the streets you hear it as voting for the lesser of two evils. The third option, of course, is to stay on the sidelines and not case a vote. Voters are, for the most part, rational, and if they choose to vote at all, they tend to vote strategically rather than symbolically. The rationalism of strategic voting over symbolic voting, coupled with the tendency for many voters to simply stay home on election day when their preferred candidate has no chance of winning, effectively marginalizes any third party movement from gaining traction in the near term.
Not all countries have this systemic pull towards two-party competition. For instance, Proportional Representation (PR) systems encourage the development of multiple parties. Here, voters choose among parties (rather than specific candidates) to represent them, and Congressional seats are allocated on the basis of the percentage of votes that the parties receive. If there are 100 seats in Congress and the Green party gets 7% of the vote, they are awarded 7 seats in Congress. This eliminates the disincentive for citizens to vote their preference, increasing party diversity AND, as a happy consequence, increasing participation (remember, third party supporters in the U.S. may choose to cast a strategic vote in place of a wasted symbolic vote, but they often simply stay home on election day). This is not to suggest that the Proportional system is better than SPMD…my purpose here is to simply explore the difference between the two systems as they relate to the presence of multiple parties. PR systems, in general, encourage multiple parties, while our SPMD system marginalizes third parties. For a detailed description, see Duverger's analysis.
For third party proponents, it is worth noting that Duverger’s Law is more a principle than a law. There are historical examples, even in this country, of third parties rising and having impact on political outcomes in SPMD systems, just as there are occasions where PR systems result in only two competitive parties. While these examples are typically exceptions rather than the rule, it is the case that systemic pressures are root-level pressures and likely must be addressed in order to make lasting change. Office-holders (i.e. those that make the rules) have little incentive to enact changes that might reduce their ability to compete for power and win. Real reform probably requires a “perfect storm” in order to overcome the slew of structural and human obstacles that are currently in place. As I’ve indicated previously, however, we may now be seeing signs of that perfect storm on the horizon.