The Mackerras Pendulum is created and named for the well known Australian political scientist and psephologist (someone who studies elections) Malcolm Mackerras. The pendulum is usually rendered as a two columned chart, with the seats held by the Government on the left side and the seats held by the Opposition on the right side (and the Crossbench seats are either listed seperately in a third column or after the Opposition seats). The seats in each column are listed in order from the smallest % swing for the opposing party/coalition to take it at the top to the largest % swing need to take the seat (or the safest seats, for short). While election swings are not uniform accross all seats, the pendulum is helpful in determining how many seats are suceptible to changing hands depending on how deep the average national swing is (or the swing in that particular state or terrritory). However, there are often cases of uneven swings, leading to safe seats that would be expected to flip remaining in the incumbent party's hands, or even a "safe" seat that somehow changes hands.

It is worth noting however, that the pendulum also takes in account when the swing to flip the seat is in reference to a third party (i.e. A Labor seat that is safe against the Coalition but under the threat of being flipped by the Greens). In this case, the party the swing is versus is listed.

While Dunkley is currently held by the Coalition and was won by them in 2016, a redistribution took place due to Victoria and ACT gaining a seat (and South Australia losing a seat; Queensland, Tasmania and Northern Territory also redistributed but did not add/lose seats). The redistribution made Dunkley on paper, a notionally Labor seat. As such, the seat on this chart is on the Coalition side as it starts with the Coalition, but with a negative percentage as the Coalition must overcome that deficit to hold the seat.