Post-election pendulum for the 2025 Australian federal election

The Australian Labor Party won the 2025 federal election in a landslide, winning 94 of 150 seats in the House of Representatives. The Coalition won 43 seats.

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'."^[1] Here, 'the vote' is defined as the vote after preferences, where the distribution of preferences has continued to the point where there are only 2 candidates left.

In the Opposition Seats table, blue is used for both the Liberal party and members of the LNP who caucus with the Liberal party room, while green is used for both the National party and members of the LNP who caucus with the National party room.

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 uses a preferential voting system such as a Condorcet method or instant-runoff voting.

The pendulum works by lining up the seats held in Parliament for the government, the opposition and the crossbenches according to the percentage point margin by which they are held on a two-candidate preferred (2CP) basis. That is also known as the swing that is required for the seat to change hands. With a uniform swing to the opposition or government parties, the number of seats changing hands can be predicted.