In Australian politics the two-party-preferred vote (TPP) is the result of an election or opinion poll after preferences have been distributed to the last two parties. For the purposes of TPP, the Liberal/National Coalition is usually considered a single party, with Labor being the other major party. Typically the TPP is expressed as the percentages of votes attracted by each of the two major parties, e.g. "Coalition 55%, Labor 45%", where the values include both primary votes and preferences. The TPP is an indicator of how much swing has been attained/is required to change the result, taking into consideration preferences, which may have a significant effect on the result.
The TPP assumes a two-party system, i.e. that after distribution of votes from less successful candidates, the two remaining candidates will be from the two major parties. However in some electorates this is not the case. The two-candidate-preferred vote (TCP) is the result after preferences have been distributed, using instant-runoff voting, to the final two candidates, regardless of which party the candidates represent. For electorates where these two candidates are from the major parties, the TCP is also the TPP. For electorates where these two candidates are not both from the major parties, preferences are notionally distributed to the two major parties to determine the TPP. In this case the TPP differs from the TCP, and is informative but has no effect on the result of the election.
The full allocation of preferences under instant-runoff voting is used in the lower houses of the Federal, Victorian, Western Australian, South Australian, and Northern Territory parliaments, as well as the upper house of Tasmania. The New South Wales lower house and Queensland use optional-preference instant runoff voting – with some votes giving limited or no preferences, TPP/TCP is not as meaningful. TPP/TCP does not occur in the Tasmanian lower house or the Australian Capital Territory due to a different system altogether, the Hare-Clark proportional voting system. Aside from Tasmania, TPP/TCP is not used in any other upper houses in Australia, with most using the group ticket single transferable proportional voting system.
Australia originally used first-past-the-post voting as used by the House of Commons of the United Kingdom. Federal election full-preference instant-runoff voting has been in existence since its introduction by the government after the 1918 Swan by-election. Candidates from the Australian Labor Party, the Nationalist Party government (predecessor to the United Australia Party and Liberal Party of Australia), and the emerging National Party of Australia (then Country Party) all received around a third of the vote, however Labor remained a few percent in front of both other candidates to win the seat. The system has allowed the two non-Labor parties to compete in many seats without splitting the conservative vote in three-cornered-contests. Even in landslide conservative election wins such as 1975 or 1996, Labor had the largest primary vote. The Coalition now comprises four parties: the Liberal Party of Australia except Queensland and the Northern Territory, the National Party of Australia in New South Wales and Victoria, the Liberal National Party of Queensland, and the Country Liberal Party in the Northern Territory. It is increasingly uncommon for seats to be contested by more than one Coalition candidate, by 2010 only three seats were contested by more than one Coalition candidate, all in New South Wales. Four seats were contested by the non-Coalition National Party of Western Australia, none were contested by the non-Coalition National Party of South Australia, and neither are automatically part of the Coalition TPP. Preferences have also been of significant relevance to the DLP, the Democrats, One Nation, the Greens, and independents.
Not distributing preferences was historically common in seats where a candidate received over 50 percent of the primary vote. Federal seat and national TPP results have only been produced as far back as 1937, though it was not uncommon in the next few decades for major parties at federal elections to not field a candidate in a few "safe" seats, but since 1972, all seats at federal elections have been contested by the major parties. Full preference distributions have occurred in all seats since 1983.
South Australian state elections have boundaries strategically redrawn before each election based on the prior TPP vote, the only state to do so. The culmination of the historical state lower house seat malapportionment known as the Playmander eventually saw it legislated after 1989 that the Electoral Commission of South Australia redraw boundaries after each election with the objective of the party that receives over 50 percent of the TPP vote at each forthcoming election forms government. Nationally in 1983/84, minor gerrymandering by incumbent federal governments was legislated against with the formation of the independent Commonwealth statutory authority, the Australian Electoral Commission.
Under the full-preference instant-runoff voting system, in each seat, the candidate with the lowest vote is eliminated and their preferences are distributed, which is repeated until only two candidates remain. Whilst every seat has a TCP result, seats where the major parties have come first and second are commonly referred to as having a TPP result. In a TCP contest between Labor and the NSW/Vic Nationals and without a Liberal candidate, this is also considered a TPP, with the Nationals in these states considered a defacto major party within the Liberal/National Coalition. In seats where the major parties do not come first and second, differing TPP and TCP results are returned. When only one of two major parties contest a seat, such as at some by-elections, only a TCP result is produced. Swings in Australian parliaments are more commonly associated with the TPP vote. At the 2010 federal election, only eight of 150 seats returned differing TPP and TCP figures ("non-classic seats"), indicating a considerable two-party system.
The tallying of seat TPP results gives a state-wide and/or national TPP vote. Non-classic seats have votes redistributed so that every seat has a TPP result. Whilst the TCP is the determining factor in deciding which candidate wins a seat, the overall election TPP is statistical and indicative only, as swings in seats are not uniform, and a varying range of factors can influence marginal seat wins with single-member electorates. Several federal elections since 1937 have seen a government elected with a minority of the TPP vote: 1940 (49.7%), 1954 (49.3%), 1961 (49.5%), 1969 (49.8%), 1990 (49.9%), and 1998 (49.0%).
As the TPP vote rather than the primary vote is a better indicator of who is in front with seats won and lost on a preferential basis, Australian opinion polls survey voter intention with a TPP always produced. However, these TPP figures tend to be calculated based on preference flows at the prior election rather than asked at the time of polling. There difference between the two is usually within the margin of error (usually +/- 3 percent). History has shown that prior election preference flows are more reliable.
Federal, Swan 1918
|Swan by-election, 1918: Division of Swan, Western Australia|
|Labor gain from Nationalist||Swing||N/A|
The result of the 1918 Swan by-election, the first-past-the-post election which caused the government of the day to introduce full-preference instant-runoff voting, under which Labor would have been easily defeated. Labor won the seat, and their majority was 3.0 percentage points (34.4 minus 31.4). No swings are available as the Nationalists retained the seat unopposed at the previous election.
Federal, Adelaide 2004
|Australian federal election, 2004: Division of Adelaide, South Australia|
|Family First||Peter G Robins||1,753||2.06||+2.06|
|Total formal votes||85,076||95.60||+0.66|
|Labor gain from Liberal||Swing||+1.95|
It can be seen that the Liberal candidate had a primary vote lead over the Labor candidate. In a first-past-the-post vote, the Liberals would have retained the seat, and their majority would be said to be 3.4 percentage points (45.3 minus 41.9).
However, under full-preference instant-runoff voting, the votes of all the minor candidates were distributed as follows:
|2nd count: Barlow 978 votes distributed|
|Family First||Peter G Robins||96||9.8||1,849||2.2|
|3rd count: Democrats 1,494 votes distributed|
|Family First||Peter G Robins||97||6.5||1,946||2.3|
|4th count: Family First 1,946 votes distributed|
|5th count: Greens 8,190 votes distributed - final TPP/TCP|
Thus, Labor defeated the Liberals, with 85 percent of Green and Green-preferenced voters preferencing Labor on the last distribution. Labor's TPP/TCP vote was 51.3 percent, a TPP/TCP majority of 1.3 points, and a TPP/TCP swing of 1.9 percent compared with the previous election.
South Australia, Frome 2009
|Frome state by-election, 2009: Electoral district of Frome, South Australia|
|Nationals SA||Neville Wilson||1,267||6.56||+6.56|
|SA Greens||Joy O'Brien||734||3.80||+0.06|
|One Nation||Peter Fitzpatrick||134||0.69||+0.69|
|Total formal votes||19,309||97.12||+0.21|
|Independent gain from Liberal||Swing||N/A|
The 2009 Frome by-election was closely contested, with the result being uncertain for over a week. Liberal leader Martin Hamilton-Smith claimed victory on behalf of the party. The result hinged on the performance of Brock against Labor in the competition for second place. Brock polled best in the Port Pirie area, and received enough eliminated candidate preferences to end up ahead of the Labor candidate by 30 votes.
|Distribution of Preferences - 4th count|
Brock received 80 percent of Labor's fifth count preferences to achieve a TCP vote of 51.72 percent (a majority of 665 votes) against the Liberal candidate. The by-election saw a rare TPP swing to an incumbent government, and was the first time an opposition had lost a seat at a by-election in South Australia. The result in Frome at the 2010 state election saw Brock come first on primary votes, increasing his primary vote by 14.1 percent to a total of 37.7 percent and his TCP vote by 6.5 percent to a total of 58.2 percent. Despite a statewide swing against Labor at the election, Labor again increased its TPP vote in Frome by 1.8 percent to a total of 50.1 percent.
Federal, Melbourne 2010
|Australian federal election, 2010: Division of Melbourne, Victoria|
|Sex Party||Joel Murray||1,633||1.83||+1.83|
|Family First||Georgia Pearson||1,389||1.55||+0.55|
|Total formal votes||89,327||96.38||–0.82|
|Greens gain from Labor||Swing||+10.75|
In this example, the two remaining candidates/parties, one a minor party, were the same after preference distribution at both this election and the previous election. Therefore, differing TPP and TCP votes, margins, and swings resulted.
South Australia, Port Adelaide 2012
|Pt Adelaide state by-election, 2012: Electoral district of Pt Adelaide, South Australia|
|Independent for You||Gary Johanson||4,717||24.3||+24.3|
|Independent True Blue Voice||Sue Lawrie||2,938||15.1||+15.1|
|Liberal Democrats||Stephen Humble||1,415||7.3||+7.3|
|SA Greens||Justin McArthur||1,096||5.6||–0.6|
|Independent Ban Live Animal Exports||Colin Thomas||314||1.6||+1.6|
|Independent Communist Australia||Bob Briton||292||1.5||+1.5|
|One Nation||Grant Carlin||269||1.4||+1.4|
|Democratic Labor||Elizabeth Pistor||151||0.8||+0.8|
|Total formal votes||19,410||92.8||–3.8|
|Independent for You||Gary Johanson||9,133||47.1||+47.1|
At the 2012 Port Adelaide state by-election, only a TCP could be produced, as the Liberal Party of Australia (and Family First Party and independent candidate Max James), who contested the previous election and gained a primary vote of 26.8 percent (and 5.9 percent, and 11.0 percent respectively), did not contest the by-election. On a TPP margin of 12.8 points from the 2010 election, considered a safe margin on the current pendulum, Labor would probably have retained their TPP margin based on unchanged statewide Newspoll since the previous election. Labor retained the seat on a 52.9 percent TCP against Johanson after the distribution of preferences.
Unlike previous examples, neither a TPP or TCP swing can be produced, as the 2010 result was between Labor and Liberal rather than Labor and independent with no Liberal candidate. An increase or decrease in margins in these situations cannot be meaningfully interpreted as swings. As explained by the ABC's Antony Green, when a major party does not contest a by-election, preferences from independents or minor parties that would normally flow to both major parties does not take place, causing asymmetric preference flows. Examples of this are the 2008 Mayo and 2002 Cunningham federal by-elections, with seats returning to TPP form at the next election. This contradicts News Ltd claims of large swings and a potential Liberal Party win in Port Adelaide at the next election.
|Primary vote||TPP vote||Seats|
|7 Sep 2013 election||33.4%||45.6%||21.1%||46.5%||53.5%||55||90||5||150|
|3–5 Sep 2013 poll||33%||46%||21%||54%||46%|
|21 Aug 2010 election||38.0%||43.3%||18.8%||50.1%||49.9%||72||72||6||150|
|17–19 Aug 2010 poll||36.2%||43.4%||20.4%||50.2%||49.8%|
|24 Nov 2007 election||43.4%||42.1%||14.5%||52.7%||47.3%||83||65||2||150|
|20–22 Nov 2007 poll||44%||43%||13%||52%||48%|
|9 Oct 2004 election||37.6%||46.7%||15.7%||47.3%||52.7%||60||87||3||150|
|6–7 Oct 2004 poll||39%||45%||16%||50%||50%|
|10 Nov 2001 election||37.8%||43.0%||19.2%||49.0%||51.0%||65||82||3||150|
|7–8 Nov 2001 poll||38.5%||46%||15.5%||47%||53%|
|3 Oct 1998 election||40.1%||39.5%||20.4%||51.0%||49.0%||67||80||1||148|
|30 Sep–1 Oct 1998 poll||44%||40%||16%||53%||47%|
|2 Mar 1996 election||38.7%||47.3%||14.0%||46.4%||53.6%||49||94||5||148|
|28–29 Feb 1996 poll||40.5%||48%||11.5%||46.5%||53.5%|
|13 Mar 1993 election||44.9%||44.3%||10.7%||51.4%||48.6%||80||65||2||147|
|11 Mar 1993 poll||44%||45%||11%||49.5%||50.5%|
|24 Mar 1990 election||39.4%||43.5%||17.1%||49.9%||50.1%||78||69||1||148|
|11 Jul 1987 election||45.8%||46.1%||8.1%||50.8%||49.2%||86||62||0||148|
|1 Dec 1984 election||47.6%||45.0%||7.4%||51.8%||48.2%||82||66||0||148|
|5 Mar 1983 election||49.5%||43.6%||6.9%||53.2%||46.8%||75||50||0||125|
|18 Oct 1980 election||45.2%||46.3%||8.5%||49.6%||50.4%||51||74||0||125|
|10 Dec 1977 election||39.7%||48.1%||12.2%||45.4%||54.6%||38||86||0||124|
|13 Dec 1975 election||42.8%||53.1%||4.1%||44.3%||55.7%||36||91||0||127|
|18 May 1974 election||49.3%||44.9%||5.8%||51.7%||48.3%||66||61||0||127|
|2 Dec 1972 election||49.6%||41.5%||8.9%||52.7%||47.3%||67||58||0||125|
|25 Oct 1969 election||47.0%||43.3%||9.7%||50.2%||49.8%||59||66||0||125|
|26 Nov 1966 election||40.0%||50.0%||10.0%||43.1%||56.9%||41||82||1||124|
|30 Nov 1963 election||45.5%||46.0%||8.5%||47.4%||52.6%||50||72||0||122|
|9 Dec 1961 election||47.9%||42.1%||10.0%||50.5%||49.5%||60||62||0||122|
|22 Nov 1958 election||42.8%||46.6%||10.6%||45.9%||54.1%||45||77||0||122|
|10 Dec 1955 election||44.6%||47.6%||7.8%||45.8%||54.2%||47||75||0||122|
|29 May 1954 election||50.0%||46.8%||3.2%||50.7%||49.3%||57||64||0||121|
|28 Apr 1951 election||47.6%||50.3%||2.1%||49.3%||50.7%||52||69||0||121|
|10 Dec 1949 election||46.0%||50.3%||3.7%||49.0%||51.0%||47||74||0||121|
|28 Sep 1946 election||49.7%||39.3%||11.0%||54.1%||45.9%||43||26||5||74|
|21 Aug 1943 election||49.9%||23.0%||27.1%||58.2%||41.8%||49||19||6||74|
|21 Sep 1940 election||40.2%||43.9%||15.9%||50.3%||49.7%||32||36||6||74|
|23 Oct 1937 election||43.2%||49.3%||7.5%||49.4%||50.6%||29||44||2||74|
|Polling conducted by Newspoll and published in The Australian. Three percent margin of error.
- National and state-by-state TPP results since 1949 - Australian Electoral Commission
- National TPP results since 1937 - Malcolm Mackerras
- "How the House of Representatives votes are counted". Australian Electoral Commission. Retrieved 11 March 2012.
- Historical national and state-by-state two-party preferred results: Australian Electoral Commission
- The Results and the Pendulum - Malcolm Mackerras: Australian National University
- Non-classic divisions, 2010 federal election: AEC
- How Should Reachtel's Ashgrove Polls be Interpreted: Antony Green ABC 10 February 2012
- "2009 Frome by-election results: State Electoral Office". Seo.sa.gov.au. Retrieved 28 July 2010.
- "2009 Frome By-election: ABC Elections". Abc.net.au. 2 February 2009. Retrieved 28 July 2010.
- "Frome by-election goes down to the wire". ABC Online. 18 January 2009. Retrieved 25 January 2009.
- Green, Antony. "Frome By-election Results". ABC Online. Retrieved 25 January 2009.
- Emmerson, Russell; Pepper, Chris (18 January 2009). "Liberals confident they'll hold Outback seat of Frome". The Advertiser. Retrieved 25 January 2009. [dead link]
- "Liberals claim victory in Frome". Poll Bludger (Crikey). 21 January 2009. Retrieved 25 January 2009. This article reproduces the original Liberal press release, no longer available on the SA Liberal site.
- Hendrik Gout (30 January 2009). "Frome one loss to another: Independent Weekly 30/1/2009". Independentweekly.com.au. Retrieved 28 July 2010.
- Richardson, Tom (30 January 2009). "Frome, a lost moment for the Libs: Independent Weekly 30/1/2009". Independentweekly.com.au. Retrieved 28 July 2010.
- "District of Frome" (PDF). Retrieved 28 July 2010.
- Pepper, Chris (25 January 2009). "Shock Frome loss rocks SA Liberals". The Advertiser. Retrieved 25 January 2009.
- Jamie Walker (31 January 2009). "Peace plea as Nationals take revenge on Liberals at polling booth: The Australian 31/1/2009". Theaustralian.news.com.au. Retrieved 28 July 2010.
- David Nason, New York correspondent (26 January 2009). "Leader left with pumpkin: The Australian 26/1/2009". Theaustralian.news.com.au. Retrieved 28 July 2010.
- Gavin Lower and David Nason (26 January 2009). "Libs demand recount after shock poll loss: The Australian 26/1/2009". Theaustralian.news.com.au. Retrieved 28 July 2010.
- Melbourne 2010 election result: AEC
- 2012 Port Adelaide by-election results: ECSA
- Port Adelaide by-election preference distribution: ECSA
- 2012 Port Adelaide by-election results: Antony Green ABC
- A Comment on the Size of the Port Adelaide Swing, Antony Green: ABC Elections 13 February 2012
- Port now a poll target for Liberals: The Advertiser 2 March 2012
- Susan Close wins Port Adelaide for Labor but seat now marginal: The Australian 11 February 2012
Labor Keeps Port Adelaide, Ramsay in South Australian by-elections: The Australian 12 February 2012
By-election swings carry 'message for Labor': The Australian 13 February 2012