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.[1]
Until 1943 non-Labor parties held the seat for all but three years. Since then, it has been consistently marginal, though it was in Labor hands for all but one term from 1943 to 1975.
Up to the 2016 election, Eden-Monaro was long regarded as Australia's most well-known "bellwether seat". From the 1972 election until the 2013 election, Eden-Monaro was won by the party that also won the election. During this time, all its sitting members were defeated at the polls – none retired or resigned.
Liberal incumbent Peter Hendy was defeated by Labor's Mike Kelly at the 2016 election. Kelly had previously represented Eden-Monaro from 2007 to 2013. Kelly's 2016 victory made him the seat's first opposition MP elected since 1969. The nation's new bellwether became the seat of Robertson – continually won by the party that also won government since the 1983 election. "Best" bellwether aside, ABCpsephologistAntony Green classed a total of eleven electorates as bellwethers in his 2016 election guide.[2]