Since 1984, federal electoral division boundaries in Australia have been determined at redistributions by a redistribution committee appointed by the Australian Electoral Commission. Redistributions occur for the boundaries of divisions in a particular state, and they occur every seven years, or sooner if a state's representation entitlement changes or when divisions of a state are malapportioned.[2]
History
When it was created it was a highly marginal seat, and at the 1972 federal election it was regarded as the "litmus seat", which the Australian Labor Party had to win to gain government. Lost when the Liberals won in 1975, Labor picked it up again when Labor regained government in 1983. However, a redistribution ahead of the following year's election made Casey marginally Liberal. The Liberals retook the seat in that election and have held it since then. Demographic changes have also contributed in making Casey a fairly safe seat for the Liberal Party, although a redistribution ahead of the 2013 federal election pushed the seat further north into the upper Yarra Valley, estimated to halve the Liberal two-party preferred majority of 4.2 per cent.[3] Since the 2023 Aston by-election, it is the Liberal Party’s safest seat in metropolitan Melbourne.