The ALP holds a five-seat majority in the House of Assembly. If the ALP loses three seats, they will lose their majority in the House. If the Liberal Party gains six seats, they will gain a majority.
The ALP has a large number of electorates held by slim margins, including five seats on margins of less than 2.5%, and eleven seats held by less than 5%.
The uniform swing needed for the Liberal Party to win a majority is 2.6%, which doesn’t sound like much until you realise that the Liberal Party already won a majority of the vote in 2010 with 51.6%, so a 2.6% swing would result in a 54.2% majority.
The five most marginal electorates include a block of four contiguous seats in the southern suburbs of Adelaide. These seats are Ashford, Bright, Elder and Mitchell. The other seat in this category is Hartley, to the east of the Adelaide city centre. Hartley is the most marginal Labor seat in the state, with a margin estimated at 0.1% for the ALP by Antony Green, a cut from 2.4% at the last election.
Most of the sitting Labor MPs in these seats are running again, except for Elder MP Patrick Conlon who is stepping down.
There are a further six Labor electorates with margins of less than 5%. Three of these seats are in a contiguous block in the north-east of Adelaide: Florey, Newland and Wright. The other seats are Light, on the northern fringe of Adelaide; Colton on the coast to the west of Adelaide; and Mawson at the southern end of Adelaide.
The campaign will be mostly focused on these eleven seats, all on the outskirts of Adelaide, including a block of five at the southern end of the city and four at the northern end of the city.
The South Australian election is likely to see a shift to the Liberal Party, but considering the relatively modest polling leads and the Liberal Party’s existing statewide margin following the 2010 election, it is also possible that marginal Liberal seats could be vulnerable.
The Liberal Party has a lot less marginal seats than the ALP: only three seats where the Liberal margin versus the ALP is less than 5%. These three seats are Adelaide, Dunstan and Morialta. All three of these seats were won by the Liberal Party in 2010, so the sitting MPs should benefit from a sophmore surge due to a new personal vote and the departure of the previous Labor MP’s personal vote.
Adelaide covers the city centre. Dunstan, which is the new name for the former electorate of Norwood, is immediately to the east of Adelaide. Neither seat underwent any change during the redistribution. Dunstan will be contested by Steven Mitchell, who has been Liberal leader since 2013. Marshall was not even a sitting MP in 2010, so his much higher profile should ensure he holds his seat. The third seat, Morialta, covers the Adelaide urban fringe to the east of the city centre.
One other seat is held by the Liberal Party by a relatively slim margin: Chaffey, along the Murray River on the state boundary. The Liberal Party defeated the sitting National MP, Karlene Maywald, in Chaffey by a 3.8% margin in 2010. On paper the seat is the safest seat in the state as a Liberal vs Labor contest. Despite the narrow margin, the Liberal Party should comfortably retain Chaffey, considering the new MP’s sophmore surge, and the fact that the National Party looks unlikely to run a strong candidate in the seat.
There is one independent-held seat which is held by a very slim margin: Mount Gambier, at the southern tip of the state. Mount Gambier was previously held by independent MP Rory McEwen from 1997 until his retirement in 2010. It has been held by independent MP Don Pegler since 2010. Pegler holds the seat by a 0.5% margin against the Liberal Party. Pegler should benefit from an increased personal vote, particularly considering that his previous role as Mayor of Grant Council did not cover the Mount Gambier urban area where most of the electorate’s population lies.