The Mackerras pendulum was devised by the Australian psephologist Malcolm Mackerras as a way of predicting the outcome of an election contested between two major parties in a Westminster style lower house legislature such as the Australian House of Representatives, which is composed of single-member electorates and which uses a preferential voting system such as a Condorcet method or IRV.
The pendulum works by lining up all of the seats held in Parliament for the government, the opposition and the crossbenches according to the percentage point margin they are held by on a two party preferred basis. This is also known as the swing required for the seat to change hands. Given a uniform swing to the opposition or government parties, the number of seats that change hands can be predicted.
Classification of seats as marginal, fairly safe or safe is applied by the independent Australian Electoral Commission using the following definition: "Where a winning party receives less than 56% of the vote, the seat is classified as 'marginal', 56–60% is classified as 'fairly safe' and more than 60% is considered 'safe'."
This Mackerras pendulum includes new notional margin estimates in Queensland, South Australia and Victoria due to boundary redistributions. The newly created Division of Bonner and Division of Gorton are also included on this pendulum with a predicted margin as no election results yet exist for both divisions.
Members in italics have declared they will not contest their seats at the election, or have lost their party's preselection.
Government seats (83)MarginalFarrerNSWSussan LeyLIB0.1 v NATSolomonNTDave TollnerCLP0.1CanningWADon RandallLIB0.4DobellNSWKen TicehurstLIB0.4AdelaideSATrish WorthLIB0.6HindmarshSAChris GallusLIB1.0ParramattaNSWRoss CameronLIB1.2PatersonNSWBob BaldwinLIB1.4HerbertQldPeter LindsayLIB1.5DeakinVicPhil BarresiLIB1.6Eden-MonaroNSWGary NairnLIB1.7RichmondNSWLarry AnthonyNAT1.7HinklerQldPaul NevilleNAT2.2McEwenVicFran BaileyLIB2.2LongmanQldMal BroughLIB2.5GippslandVicPeter McGauranNAT2.6MoretonQldGary HardgraveLIB2.6PageNSWIan CausleyNAT2.8McMillanVicChristian ZahraLIB2.9BowmanQldCon SciaccaLIB3.1PetrieQldTeresa GambaroLIB3.5La TrobeVicBob CharlesLIB3.7MakinSATrish DraperLIB3.7KalgoorlieWABarry HaaseLIB4.3CowperNSWLuke HartsuykerNAT4.7DunkleyVicBruce BillsonLIB5.2CorangamiteVicStewart McArthurLIB5.4LindsayNSWJackie KellyLIB5.5WarringahNSWTony AbbottLIB5.7 v INDFairly safeAstonVicChris PearceLIB6.0DicksonQldPeter DuttonLIB6.0MooreWAMal WasherLIB6.0LeichhardtQldWarren EntschLIB6.4BlairQldCameron ThompsonLIB6.6PearceWAJudi MoylanLIB6.9FordeQldKay ElsonLIB7.0RobertsonNSWJim LloydLIB7.0CaseyVicTony SmithLIB7.2BoothbySAAndrew SouthcottLIB7.4FlindersVicGreg HuntLIB7.4ForrestWAGeoff ProsserLIB7.6BennelongNSWJohn HowardLIB7.7WentworthNSWPeter KingLIB7.9DawsonQldDe-Anne KellyNAT8.0TangneyWADaryl WilliamsLIB8.0HigginsVicPeter CostelloLIB8.4SturtSAChristopher PyneLIB8.5MacquarieNSWKerry BartlettLIB8.7ParkesNSWJohn CobbNAT8.7MenziesVicKevin AndrewsLIB8.9FairfaxQldAlex SomlyayLIB9.2WannonVicDavid HawkerLIB9.2GoldsteinVicDavid KempLIB9.5RyanQldMichael JohnsonLIB9.5HumeNSWAlby SchultzLIB9.8Wide BayQldWarren TrussNAT9.9SafeMacarthurNSWPat FarmerLIB10.0HughesNSWDanna ValeLIB10.4GreySABarry WakelinLIB10.6IndiVicSophie PanopoulosLIB10.7KooyongVicPetro GeorgiouLIB10.9LyneNSWMark VaileNAT11.2FisherQldPeter SlipperLIB11.8McPhersonQldMargaret MayLIB12.2FaddenQldDavid JullLIB13.1North SydneyNSWJoe HockeyLIB13.2CurtinWAJulie BishopLIB13.9CookNSWBruce BairdLIB14.0MayoSAAlexander DownerLIB14.3GilmoreNSWJoanna GashLIB14.6GwydirNSWJohn AndersonNAT14.9GroomQldIan MacfarlaneLIB15.1MaranoaQldBruce ScottNAT15.4BerowraNSWPhilip RuddockLIB15.7MoncrieffQldSteven CioboLIB16.3BarkerSAPatrick SeckerLIB16.6MackellarNSWBronwyn BishopLIB16.9O'ConnorWAWilson TuckeyLIB19.1MalleeVicJohn ForrestNAT20.9BradfieldNSWBrendan NelsonLIB21.2MitchellNSWAlan CadmanLIB21.3MurrayVicSharman StoneLIB21.9RiverinaNSWKay HullNAT29.9 Opposition seats (63) MarginalBrisbaneQldArch BevisALP1.0KingstonSADavid CoxALP1.3WakefieldSANeil AndrewALP1.3StirlingWAJann McFarlaneALP1.6HasluckWASharryn JacksonALP1.8BonnerQldNew divisionALP1.9SwanWAKim WilkieALP2.0BassTasMichelle O'ByrneALP2.1RankinQldCraig EmersonALP2.4ChisholmVicAnna BurkeALP2.7BanksNSWDaryl MelhamALP2.9GreenwayNSWFrank MossfieldALP3.1BallaratVicCatherine KingALP3.2BendigoVicSteve GibbonsALP3.6LoweNSWJohn MurphyALP3.8LilleyQldWayne SwanALP4.6JagajagaVicJenny MacklinALP5.3LingiariNTWarren SnowdonALP5.3CapricorniaQldKirsten LivermoreALP5.5CowanWAGraham EdwardsALP5.5Melbourne PortsVicMichael DanbyALP5.7Fairly safeBartonNSWRobert McClellandALP6.0BraddonTasSid SidebottomALP6.0GriffithQldKevin RuddALP6.2BruceVicAlan GriffinALP6.5IsaacsVicAnn CorcoranALP6.6CharltonNSWKelly HoareALP6.7NewcastleNSWSharon GriersonALP6.9HoltVicAnthony ByrneALP7.9FranklinTasHarry QuickALP8.0OxleyQldBernie RipollALP8.0LyonsTasDick AdamsALP8.2CorioVicGavan O'ConnorALP8.5WerriwaNSWMark LathamALP8.5ShortlandNSWJill HallALP8.8Kingsford SmithNSWLaurie BreretonALP8.9CanberraACTAnnette EllisALP9.4SafeBrandWAKim BeazleyALP10.1FremantleWACarmen LawrenceALP10.7HunterNSWJoel FitzgibbonALP10.9HothamVicSimon CreanALP11.0PerthWAStephen SmithALP11.2LalorVicJulia GillardALP12.1ProspectNSWJanice CrosioALP12.8FraserACTBob McMullanALP13.0DenisonTasDuncan KerrALP14.3SydneyNSWTanya PlibersekALP15.0CalwellVicMaria VamvakinouALP15.1ThrosbyNSWJennie GeorgeALP15.1BlaxlandNSWMichael HattonALP15.2ChifleyNSWRoger PriceALP15.3MaribyrnongVicBob SercombeALP15.4Port AdelaideSARod SawfordALP16.0ReidNSWLaurie FergusonALP16.9WatsonNSWLeo McLeayALP17.3MelbourneVicLindsay TannerALP19.9GortonVicNew divisionALP20.2ScullinVicHarry JenkinsALP20.3GellibrandVicNicola RoxonALP20.4WillsVicKelvin ThomsonALP20.6GrayndlerNSWAnthony AlbaneseALP21.3FowlerNSWJulia IrwinALP21.5BatmanVicMartin FergusonALP25.1 Crossbench seats (4)CunninghamNSWMichael OrganGRN2.2 v ALPNew EnglandNSWTony WindsorIND8.3 v NATKennedyQldBob KatterIND14.1 v ALPCalareNSWPeter AndrenIND25.0 v NAT
Notes Although the seats of Bowman and McMillan were Labor wins at the previous election, the redistributions in Queensland and Victoria changed them to notionally marginal Liberal seats.
Con Sciacca was not contesting Bowman in the 2004 election, but rather transferring to contest Bonner instead.
Although the seat of Wakefield was won by the Liberals at the previous election, the redistribution in South Australia changed it to be a notionally marginal Labor seat.
Michael Organ was elected in a (b/e) with a margin of 2.2%
See also 2004 Australian federal election 2001 Australian House of Representatives election Senate results for the Australian federal election, 2001 Members of the Australian House of Representatives, 2001–2004 Post-election pendulum for the 2001 Australian federal election
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