The following Mackerras pendulum shows the notional margins for seats following boundary redistributions in Victoria, Queensland, South Australia, Tasmania, the Northern Territory and the ACT. Based on ABC analyst Antony Green's calculations of the effect of boundary redistributions for the next election,[1] and the outcome of the 2018 Wentworth by-election, the pendulum has the Coalition government on 73 of 151 seats with the Labor opposition on 72 seats and a crossbench of six seats.[1]
Assuming a theoretical nationwide uniform swing, the Labor opposition would need at least 50.7% of the two-party vote (at least a 1.1-point two-party swing) to win 76 seats and majority government. The incumbent Coalition government no longer holds a majority, and would require at least 51.1% of the two-party vote (at least a 0.7-point two-party swing) to regain it.
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'."[2]
a Although the seats of Corangamite and Dunkley were Liberal wins at the previous election, the redistribution in Victoria changed them to notionally marginal Labor seats.
b Julia Banks won Chisholm as a Liberal candidate, and quit the Liberal party to sit as an Independent. She is not recontesting Chisholm, but she is instead contesting Flinders.
c Bean entirely consists of area from the pre-redistribution Canberra and can be considered a renaming of the seat, while the post redistribution seat of Canberra contains approximately as many voters from pre-redistribution Fenner as Canberra, and can be considered a new seat.
