South Australia’s electoral boundaries are redrawn after every election. The boundaries have been dramatically redrawn since the 2014 election, with only one seat left untouched. This reflects the result of the last election, where the Liberal Party won a majority of the two-party-preferred vote but failed to win government, and a state constitution which requires the mapmakers to remedy this result in their boundaries.
At the 2014 election, Labor won 23 seats in the House of Assembly, along with 22 Liberals and two independents. Labor subsequently won a 24th seat at the 2014 Fisher by-election. On the new boundaries, the Liberal Party holds 26 seats, compared to 20 for Labor, and one independent. This was a net change of four seats.
46 out of 47 seats were modified. Mount Gambier, at the state’s south-eastern tip, was the only electorate left unchanged.
When comparing the 2014 election margins to the notional post-redistributions margins, the changes are quite stark. Only eleven seats had a margin change of less than 0.5%.
Seven seats had a change in margin of over 5%.
There were four seats which changed from Labor to Liberal:
- Colton – 1.6% ALP changed to 3.7% LIB
- Elder – 1.9% ALP changed to 4.3% LIB
- Mawson – 5.7% ALP changed to 3.2% LIB
- Newland – 1.5% ALP changed to 0.1% LIB
These major changes were required due to the South Australian state constitution, which required “fairness” in the drawing of electoral boundaries. This was defined as producing electoral boundaries which would give a party a majority of seats if they won a majority of the two-party-preferred vote. This clause was recently removed from the constitution.