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 (78)MarginalStirlingWARon EdwardsALP0.2RichmondNSWNeville NewellALP0.5PageNSWHarry WoodsALP0.7CowanWACarolyn JakobsenALP0.9KennedyQldRob HullsALP1.4CanningWAGeorge GearALP1.8FisherQldMichael LavarchALP2.0Melbourne PortsVicClyde HoldingALP2.1MoretonQldGarrie GibsonALP2.3PetrieQldGary JohnsALP2.3CunninghamNSWStewart WestALP2.4 v DEMSwanWAKim BeazleyALP2.4MakinSAPeter DuncanALP2.4JagajagaVicPeter StaplesALP2.6RobertsonNSWFrank WalkerALP2.8BartonNSWGary PunchALP3.1BurkeVicNeil O'KeefeALP3.3CalareNSWDavid SimmonsALP3.5LeichhardtQldJohn GaylerALP3.5AdelaideSABob CatleyALP3.7HinklerQldBrian CourticeALP4.0CorioVicGordon ScholesALP4.2HothamVicSimon CreanALP4.2Eden-MonaroNSWJim SnowALP4.3FordeQldMary CrawfordALP4.5HerbertQldTed LindsayALP4.9KingstonSAGordon BilneyALP5.0Northern TerritoryNTWarren SnowdonALP5.0BrandWAWendy FatinALP5.2PerthWARic CharlesworthALP5.2HindmarshSAJohn ScottALP5.3BrisbaneQldArch BevisALP5.5RankinQldDavid BeddallALP5.5CanberraACTRos KellyALP5.8Fairly safeDenisonTasDuncan KerrALP6.4GreySALloyd O'NeilALP6.5HughesNSWRobert TicknerALP6.6PhillipNSWJeannette McHughALP6.6HoltVicMichael DuffyALP6.9CalwellVicAndrew TheophanousALP7.1MaribyrnongVicAlan GriffithsALP7.2CapricorniaQldKeith WrightALP7.3BowmanQldCon SciaccaALP7.5LilleyQldElaine DarlingALP7.7St GeorgeNSWStephen DuboisALP7.8BanksNSWDaryl MelhamALP7.9WillsVicBob HawkeALP7.9ParramattaNSWPaul ElliottALP8.3FremantleWAJohn DawkinsALP8.3HunterNSWEric FitzgibbonALP8.4GreenwayNSWRuss GormanALP8.8LalorVicBarry JonesALP9.0ScullinVicHarry JenkinsALP9.4SafeLindsayNSWRoss FreeALP10.1ThrosbyNSWColin HollisALP10.2KalgoorlieWAGraeme CampbellALP10.2GriffithQldBen HumphreysALP10.3DobellNSWMichael LeeALP10.6FraserACTJohn LangmoreALP11.3OxleyQldLes ScottALP12.0BlaxlandNSWPaul KeatingALP12.2MacarthurNSWStephen MartinALP12.7NewcastleNSWAllan MorrisALP12.8 v INDGrayndlerNSWLeo McLeayALP13.3Port AdelaideSARod SawfordALP13.3ProspectNSWJanice CrosioALP14.0WerriwaNSWJohn KerinALP14.0FowlerNSWTed GraceALP14.2ShortlandNSWPeter MorrisALP14.3Kingsford SmithNSWLaurie BreretonALP15.0CharltonNSWBob BrownALP15.7BonythonSANeal BlewettALP15.9ReidNSWLaurie FergusonALP16.1BatmanVicBrian HoweALP17.4MelbourneVicGerry HandALP17.5GellibrandVicRalph WillisALP18.5Very safeChifleyNSWRoger PriceALP20.1SydneyNSWPeter BaldwinALP21.4 Opposition seats (69)MarginalHawkerSAChris GallusLIB0.01DawsonQldRay BraithwaiteNAT0.1LoweNSWBob WoodsLIB0.6CorinellaVicRussell BroadbentLIB0.7BendigoVicBruce ReidLIB1.1DunkleyVicFrank FordLIB1.2La TrobeVicBob CharlesLIB1.4BallaratVicMichael RonaldsonLIB1.9FranklinTasBruce GoodluckLIB2.1LyonsTasMax BurrLIB2.1DeakinVicKen AldredLIB2.4McEwenVicFran BaileyLIB3.2MacquarieNSWAlasdair WebsterLIB3.6FaddenQldDavid JullLIB3.8BassTasWarwick SmithLIB4.3GilmoreNSWJohn SharpNAT4.4McMillanVicJohn RiggallLIB4.4Riverina-DarlingNSWNoel HicksNAT4.5AstonVicPeter NugentLIB4.6Wide BayQldWarren TrussNAT4.9FlindersVicPeter ReithLIB5.2IsaacsVicRod AtkinsonLIB5.7GoldsteinVicDavid KempLIB6.0Fairly safeNew EnglandNSWIan SinclairNAT6.3ChisholmVicMichael WooldridgeLIB6.3MooreWAPaul FilingLIB6.9WentworthNSWJohn HewsonLIB7.2RyanQldJohn MooreLIB7.2CookNSWDon DobieLIB7.3CowperNSWGarry NehlNAT7.3LyneNSWBruce CowanNAT7.3FairfaxQldAlex SomlyayLIB7.5SturtSAIan WilsonLIB7.7HumeNSWWal FifeLIB8.2CaseyVicBob HalversonLIB8.2BraddonTasChris MilesLIB8.4PearceWAFred ChaneyLIB8.9DundasNSWPhillip RuddockLIB9.3BruceVicJulian BealeLIB9.3MoncrieffQldKathy SullivanLIB9.5WarringahNSWMichael MacKellarLIB9.9ForrestWAGeoff ProsserLIB9.9SafeBennelongNSWJohn HowardLIB10.3ParkesNSWMichael CobbNAT10.7BoothbySASteele HallLIB10.7CorangamiteVicStewart McArthurLIB10.8McPhersonQldJohn BradfordLIB11.0MackellarNSWJim CarltonLIB11.1GwydirNSWJohn AndersonNAT11.2MayoSAAlexander DownerLIB11.6HigginsVicPeter CostelloLIB11.8TangneyWAPeter ShackLIB11.8GroomQldBill TaylorLIB12.2WannonVicDavid HawkerLIB12.7BerowraNSWHarry EdwardsLIB12.8CurtinWAAllan RocherLIB12.8WakefieldSANeil AndrewLIB12.9MaranoaQldBruce ScottNAT13.2BarkerSAIan McLachlanLIB13.6IndiVicEwen CameronLIB14.2MenziesVicNeil BrownLIB14.3KooyongVicAndrew PeacockLIB14.8FarrerNSWTim FischerNAT17.8GippslandVicPeter McGauranNAT18.9Very safeMitchellNSWAlan CadmanLIB20.3O'ConnorWAWilson TuckeyLIB21.9BradfieldNSWDavid ConnollyLIB22.3MurrayVicBruce LloydNAT23.3MalleeVicPeter FisherNAT23.8Crossbench seats (1)North SydneyNSWTed MackIND7.7 v LIB

References