Currently in Australia, there are two major parties: The Australian Labor Party and the Australian Liberal Party (which ironically is a conservative party. Currently in Australia it is simply not possible for someone to become Prime Minister if they do not represent one of these political parties.

My question is this: Why does Australia have this two-party system, How did it become this way, and How many other developed countries have a two-party system?

  • First-Past-The-Post/winner-takes-all versus Proportional Representation. Speaking of which, the Senate of Australia uses proportional representation, and the House does not, yet the House is more diverse (reason?, more seats?)
    – user1873
    Commented Sep 22, 2013 at 14:04
  • This year's election is a perfect example of how the Seanate has been far more diverse. These results show it.
    – user2076
    Commented Sep 22, 2013 at 14:06
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    Forgive me if I have misstated the facts. Not being an Australian, I could not care less about Australian politics. perhaps TPP voting is the answer?
    – user1873
    Commented Sep 22, 2013 at 14:16
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    Who could blame you. The two party preferred system actually seems like a good explanation because the preferences always wind up going to a major party.
    – user2076
    Commented Sep 22, 2013 at 14:18
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    Incorrect premise: Australia isn't a two-party system, never has been, and likely never will due to electoral structure. At Federation Australia possessed Protectionists, Free Traders, and Labor. Then there were Rural anti-labour Parties and Urban anti-labour Parties and Labor and Labor Rats (of three kinds). Then the CPA became viable in industry. By the time the CPA was failing in industry, a party of Wet Liberals formed, and by the time the CPA failed, the Greens existed. On top of this Rural Independents and occasional Labour independents have existed. Question is wrong: unanswerable Commented Oct 8, 2013 at 20:24

1 Answer 1


This is not limited to Australia, but rather a by-product of any legislature whose members are selected through plurality voting (a/k/a winner takes all).

The phenomena is called Duverger's Law.

To summarise the process:

  1. Everyone has nuanced life experiences and separate subtle opinions on law and policy. In the absence of direct democracy, these opinions are aggregated into groups of (presumably) compatible opinions so that more people will roughly support a representative striving to enact those opinions.
  2. At first these groups (parties) are fairly diverse and certainly more than just two groups. But after each winner-take-all election for an electorate's representative, the parties with least support realise they will never get voted in as their mind-share is too low. So their supporters vote for the closest popular party with roughly compatible policies. The failed party can be considered as 'destroyed' or 'merged into' the successful party.
  3. This occurs successively over multiple electoral cycles until all diversity and subtlety of opinion collapses into two parties - each full of sweeping useless generalisations and ideological cant.

Or put another way, people don't usually vote for a party that will have no influence in policy. Unless minority coalition governments were explicitly encouraged from the outset; established majority parties will discourage and disparage minority governments since the major parties would prefer to rule less often but completely, than rule more often but share power.

It really comes down to whether ideological reconciliation should happen within the murky internal shadows of each major party or in broad daylight between representatives.

C.G.P Grey has an excellent YouTube video on the problem of plurality voting: http://www.youtube.com/watch?v=s7tWHJfhiyo

Regarding the decision of whether Australia specifically is or isn't a two party system:

A distinction has to be made between the House and Senate.

The Senate has a limited level of proportional representation and so ideological reconciliation occurs in the senate chamber (a good thing) instead within the voting booth as some form of game-theory trying to optimise between two viable options (e.g. Tolerable Party vs Intolerable Party). So we consider the Senate a "multi-party" chamber.

The House is representative in a geographical sense. So each electorate will collapse into two parties; but each electorate may have different political priorities.

However, since major parties are more willing (one supposes) to listen to representatives of their own party than other representatives - representatives are incentivised to belong to (be endorsed by) a major party than be locked out in the cold. Voters vote with much the same rational, so each major party gains national homogeneity and reach - with the expectation of reconciling any geographic differences opaquely and internally within the party.

The instant-runoff voting for the House upsets the apple cart if and only if one of the major parties fails to be broad-based enough to siphon off third party policies in a given electorate (i.e. a majority party swaps places with a minority party).

This is typically hard for a minority party to do - as just like any independent candidate - you can't sell that you will have actual impact unless you really do hold the balance of power in House. This is much rarer in the House than in the Senate given that the very nature of plurality voting provides House landslides to most ruling governments. So if you see any cross-bench MPs in the House, then one or both major parties has a broken base; or rogue members that were disendorsed.

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    Australia has STV and multi-member STV voting, not FPTP voting. Characterising this state as "winner takes all," is wrong. The answer also fails to account for long running regional and sectional politics in Australia, including the Country Party, DLP, and Independent Labour. This answer is simply wrong. Commented Oct 9, 2013 at 7:52
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    @SamuelRussell I'm getting little tired of downvotes and blanket statements of "Wrong!" from someone fond of applying Ignoratio Elenchi and the Fallacy of Division on other people's answers. You know perfectly well that STV only applies to the Senate; which does not provide the PM or the two-party system. The IRV used in the House is a winner-take-all system that auto-collapses to the same plurality vote result if the actors had had perfect information. For the purpose of Duverger's Law it is same. Commented Oct 9, 2013 at 8:21
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    @SamuelRussell Your ability to progressively update your comment notwithstanding (original: "Australia has STV and multi-member STV voting, not FPTP voting. This answer is simply wrong."), I don't need to "factor in" regional and sectional politics to explain why we have a two-party federal system; as the ILP is defunct, the DLP has no House seats, and the word 'Country' could apply to half of all the defunct or subsumed parties in history - of which "The" Country Party was rebadged The National Party and absorbed into the Liberal Coalition in a manner in line with the two-party paradigm. Commented Oct 9, 2013 at 8:37
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    I'm sorry, the question doesn't say from the md nineties or with really capricious analysis of anti-labour politics or the reduction of Australian politics to the federal parliament. You stretched so far you broke the bow. Commented Oct 9, 2013 at 10:26
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    Last time I checked Australia wasn't Queensland, and the Nationals maintained an independent policy line. So much so that a minister was disciplined in the first few days of a new government. If you wan't to go around bending "party" until it breaks as a theoretical term feel free without actually noting your unique and personal definition. Your answer isn't in contact with the empirical data. Commented Oct 9, 2013 at 21:18

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