The Mackerras pendulum 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 instant-runoff voting.

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.

Government seats (94)MarginalNorthern TerritoryNTNick DondasCLP0.37PatersonNSWBob BaldwinLIB0.43CanningWARicky JohnstonLIB0.69LilleyQldElizabeth GraceLIB0.73BendigoVicBruce ReidLIB0.88BowmanQldAndrea WestLIB0.89MakinSATrish DraperLIB1.08La TrobeVicBob CharlesLIB1.37GriffithQldGraeme McDougallLIB1.47LindsayNSWJackie KellyLIB1.58KingstonSASusan JeanesLIB2.01McMillanVicRussell BroadbentLIB2.07McEwenVicFran BaileyLIB2.18CowanWARichard EvansLIB2.39LoweNSWPaul ZammitLIB2.47DeakinVicPhil BarresiLIB2.48ChisholmVicMichael WooldridgeLIB2.59DicksonQldTony SmithLIB3.17DunkleyVicBruce BillsonLIB3.36AdelaideSATrish WorthLIB3.52RobertsonNSWJim LloydLIB3.56CapricorniaQldPaul MarekNAT3.62BallaratVicMichael RonaldsonLIB3.67MurrayVicSharman StoneLIB3.70 v NATSwanWADon RandallLIB3.71ParramattaNSWRoss CameronLIB3.87LeichhardtQldWarren EntschLIB4.18PageNSWIan CausleyNAT4.31BassTasWarwick SmithLIB4.57Eden-MonaroNSWGary NairnLIB4.76HughesNSWDanna ValeLIB4.89MoretonQldGary HardgraveLIB5.09StirlingWAEoin CameronLIB5.17AstonVicPeter NugentLIB5.59BraddonTasChris MilesLIB5.70Fairly safeGilmoreNSWJoanna GashLIB6.24MacquarieNSWKerry BartlettLIB6.36ParkesNSWMichael CobbNAT6.50HerbertQldPeter LindsayLIB6.59CaseyVicBob HalversonLIB6.65RichmondNSWLarry AnthonyNAT6.75CorangamiteVicStewart McArthurLIB7.69PetrieQldTeresa GambaroLIB7.70WentworthNSWAndrew ThomsonLIB7.83HindmarshSAChris GallusLIB8.06GreySABarry WakelinLIB8.54FordeQldKay ElsonLIB9.70DawsonQldDe-Anne KellyNAT9.92SturtSAChristopher PyneLIB9.99SafeFlindersVicPeter ReithLIB10.07BennelongNSWJohn HowardLIB10.13HinklerQldPaul NevilleNAT10.36MacarthurNSWJohn FaheyLIB10.69HigginsVicPeter CostelloLIB10.73GoldsteinVicDavid KempLIB10.94MenziesVicKevin AndrewsLIB10.99CowperNSWGarry NehlNAT11.56LongmanQldMal BroughLIB11.59BoothbySAAndrew SouthcottLIB11.60HumeNSWAlby SchultzLIB11.77TangneyWADaryl WilliamsLIB12.13PearceWAJudi MoylanLIB12.18CookNSWStephen MutchLIB12.28WannonVicDavid HawkerLIB12.31ForrestWAGeoff ProsserLIB13.64KooyongVicPetro GeorgiouLIB13.81KennedyQldBob KatterNAT14.49MayoSAAlexander DownerLIB15.16WarringahNSWTony AbbottLIB15.32LyneNSWMark VaileNAT15.44North SydneyNSWJoe HockeyLIB15.56MackellarNSWBronwyn BishopLIB16.53RyanQldJohn MooreLIB16.87McPhersonQldJohn BradfordLIB17.00IndiVicLou LiebermanLIB17.79FaddenQldDavid JullLIB17.84FairfaxQldAlex SomlyayLIB18.09BerowraNSWPhilip RuddockLIB18.40GwydirNSWJohn AndersonNAT18.51Wide BayQldWarren TrussNAT18.53GippslandVicPeter McGauranNAT18.64New EnglandNSWIan SinclairNAT19.18WakefieldSANeil AndrewLIB19.96Very safeMoncrieffQldKathy SullivanLIB20.25FisherQldPeter SlipperLIB20.34BarkerSAIan McLachlanLIB20.89RiverinaNSWNoel HicksNAT21.01FarrerNSWTim FischerNAT21.23GroomQldBill TaylorLIB21.28MalleeVicJohn ForrestNAT23.50MitchellNSWAlan CadmanLIB24.32MaranoaQldBruce ScottNAT25.73BradfieldNSWBrendan NelsonLIB25.77O'ConnorWAWilson TuckeyLIB25.93 Opposition seats (49)MarginalDobellNSWMichael LeeALP0.08BrandWAKim BeazleyALP0.23BrisbaneQldArch BevisALP0.36BruceVicAlan GriffinALP0.76LyonsTasDick AdamsALP1.31RankinQldDavid BeddallALP1.35BanksNSWDaryl MelhamALP1.41NamadgiACTAnnette EllisALP1.51IsaacsVicGreg WiltonALP1.56JagajagaVicJenny MacklinALP2.71GreenwayNSWFrank MossfieldALP3.39FremantleWACarmen LawrenceALP4.25BartonNSWRobert McClellandALP4.34FranklinTasHarry QuickALP4.68WillsVicKelvin ThomsonALP5.77 v INDFairly safeMelbourne PortsVicClyde HoldingALP6.05WerriwaNSWMark LathamALP6.21PerthWAStephen SmithALP6.46CorioVicGavan O'ConnorALP6.80HunterNSWJoel FitzgibbonALP6.97ChisholmVicNeil O'KeefeALP7.03Port AdelaideSARod SawfordALP7.05FraserACTJohn LangmoreALP7.32CanberraACTBob McMullanALP7.52ShortlandNSWPeter MorrisALP8.15CharltonNSWKelly HoareALP9.32BonythonSABob BrownALP9.32SafeKingsford SmithNSWLaurie BreretonALP10.15HothamVicSimon CreanALP10.56NewcastleNSWAllan MorrisALP11.19ReidNSWLaurie FergusonALP11.38WatsonNSWLeo McLeayALP11.68DenisonTasDuncan KerrALP11.79HoltVicGareth EvansALP12.81CunninghamNSWStephen MartinALP12.91BlaxlandNSWPaul KeatingALP12.98SydneyNSWPeter BaldwinALP13.80ProspectNSWJanice CrosioALP13.91ChifleyNSWRoger PriceALP14.54GrayndlerNSWAnthony AlbaneseALP16.38CalwellVicAndrew TheophanousALP17.19FowlerNSWTed GraceALP18.27LalorVicBarry JonesALP18.51MaribyrnongVicBob SercombeALP18.85ThrosbyNSWColin HollisALP19.62Very safeMelbourneVicLindsay TannerALP20.21ScullinVicHarry JenkinsALP20.74GellibrandVicRalph WillisALP21.23BatmanVicMartin FergusonALP21.31Crossbench seats (5)OxleyQldPauline HansonIND4.66 v ALPCurtinWAAllan RocherIND7.28 v LIBCalareNSWPeter AndrenIND13.32 v NATKalgoorlieWAGraeme CampbellIND10.35 v ALPMooreWAPaul FilingIND15.48 v ALP

References