Two-party system
A two-party system is a type of party system where only two political parties have a realistic chance of winning an election. Usually this means that the candidates of the two parties that get the most votes hold all, or nearly all, elected offices. Coalition governments occur only rarely in two-party systems, though each party may internally look like a coalition.
The concept of "winning" multi-member elections appears intertwined with the predominance of thinking along two-party system lines, because it is rare for a single party to "win" (that is, gain over 50% of seats in) elections in a multi-party system.
How/why it occurs
Two-party systems often develop spontaneously when the voting system used for elections discriminates against third or smaller parties, because the number of votes received for a party in a whole country does not relate directly and proportionally to the number of seats it receives in the country's assembly/assemblies. The most widely-used system to have this effect, the simple plurality system (first past the post) often appears to pull systems into encouraging the survival of only two major parties: a third force can break in on the scene (the Labour Party in 20th-century Britain, or the Republican Party in the 19th-century United States, for example) but only at the ultimate expense of a former major party (the Liberal Party in Britain, the Whigs in the USA respectively). The overall system re-stabilizes into two-party mode after a three-party interlude - see Duverger's law.
Some representation systems - such as those involving a single elected president or a mayor dominating the government - may encourage two-party systems, since ultimately the contest will pit the two most popular candidates against each other.
When constituencies (districts) vote for candidates on the basis of a geographical constituency, all votes for candidates other than the winner count for nothing. This reflects another factor that encourages a two party system: because smaller parties often cannot win enough votes in a constituency because they have smaller support and sometimes more scattered support than larger parties. Often a first-past-the-post electoral system and the election of candidates from geographical constituencies (districts) appear together in a single political system: this means that some smaller parties can garner a significant proportional of votes nationally, but receive few constituency seats and thus cannot realistically expect to compete overall on an equal footing with larger country-wide parties.
In countries that use proportional representation (PR), especially where the whole country forms a single constituency (like Israel), the electoral rules discourage a two-party system; the number of votes received for a party relates directly and proportionally to the number of representative seats won, and new parties can thus develop an immediate electoral niche. Duverger identified that the use of proportional representation would make a two party system less likely. However, other systems do not guarantee new parties access to the system: Malta provides an example of a stable two-party system using the single transferable vote.
Often, two-party systems result from various factors, mostly the use of a first-past-the-post voting system, rather than from deliberate electoral/political engineering.
Examples
Two-party system have historically occurred commonly in the so-called Anglosphere nations such as the United Kingdom and former British colonies like Jamaica, New Zealand and the United States. While Americans and Britons often see the two-party system as natural, based on their long experiences with it, it in fact comes about as a product of particular rules and conventions (especially those involving first-past-the-post voting). The two parties that dominate at any particular time thus have an incentive to keep the existing rules in operation, so as to prevent electoral erosion to the benefit of smaller parties.
Advantages and problems
The two-party system's defenders argue that:
- Uncommon, unconventional ideas and ideologies remain non-influential, so policies and governments do not change rapidly. (Others dispute whether such innate conservatism provides advantages. While smaller parties find this exceptionally frustrating, proponents of the two-party system suggest that it enhances stability while eventually allowing for ideas that gain favor to become politically influential.)
- The dynamics of a two-party system drives both parties' policies towards the position of a mythical median voter while remaining (hopefully) distinctive enough to motivate their core support.
- Two-party systems, especially those where power often changes hands, appear less prone to revolutions, coups, or civil wars.
Against the argument that the two-party system leads to more stable governance, critics of two-party systems argue variously that:
- Stability is not desirable in itself.
- The two-party system does produce stable governments, but this comes at the expense of the preferred outcome of stable democracy.
- Two-party systems do not appear intrinsically any more stable, citing such examples of stable democracies as Canada or Germany (which has a multi-party system through proportional representation).
Observers also criticise two-party systems for the following alleged flaws:
- Simplified (virtual two-way elections) motivate candidates to run negative campaigns, pointing out the flaws in the "other person" (usually the leader of the other party). Parties in such situations tend to stake out only those positions that appear necessary to differentiate themselves from their primary opponent, and not to concentrate on policies constructive or beneficial to citizens.
- If one of the two parties becomes weak, a dominant-party system may develop.
- Debate in the assembly of the country can often become adversarial and not constructive, sometimes revolving around narrowly-perceived policy ideas, rather than larger political issues. Sometimes adversarial politics can lead to the opposition disagreeing with everything the government proposes (and vice versa) for the sake of disagreeing. This can lead to the blocking of important legislation, especially reforms that may benefit the country.
- Campaign contributions can more easily corrupt a two-party system - since it has fewer players to receive donations.
- In an effort to attract voters, each party will adopt planks of the other party's platform, leading to the appearance in some skeptics' minds of a one-party system. Examples include the American notion of a "Republicrat".
- First-past-the-post election systems tend to produce fewer female and minority representatives than proportional representation systems.
- Elections based on geographical district representation can become subject to gerrymander. Even without deliberate partisan gerrymander, legislative representation can skew wildly from the actual percentage of the vote a party wins. In two 20th-century British elections, for example, the party with the second-highest total vote tally actually won a parliamentary majority.
The electoral systems which tend to favour two-party systems (notably the "biggest pile of votes wins" system) also receive criticism because:
- Most electors have perforce to engage in tactical voting, voting for candidates that may not be their first choice - either to help a perceived potential "winner" or to block a potential enemy.
- Smaller parties suffer from under-representation: they will not receive a number of seats in the country's assembly that reflects the number of votes they receive (and therefore the amount of support they could or do receive). Some see this as undemocratic, arguing that citizens who vote for small parties should receive fair representation.
- Smaller parties often represent unconventional or 'alternative' (compared to the main parties) ideologies and formulate policy on the basis of such ideologies. Some comentators argue that in a democracy, all supported ideologies should receive fair representation.
- Larger parties benefit from over-representation; some see this as undemocratic.