6 December. Labor's Nat Cook won the by-election by nine votes with a 7.3 percent two-party swing against the Liberals, resulting in a change from minority to majority government. On a 0.02 percent margin it is the most marginal seat in parliament. Despite this, the Weatherill Labor government kept crossbench MPs Geoff Brock and Martin Hamilton-Smith in cabinet, giving the government a 26 to 21 parliamentary majority. ABC psephologist Antony Green described the by-election as a "very bad result for the Liberal Party in South Australia" both state and federally, and that a fourth term government gaining a seat at a by-election is unprecedented in Australian history. Liberal Iain Evans in Davenport resigned from parliament on 30 October 2014 which triggered a 2015 Davenport by-election for 31 January. Liberal Sam Duluk won the seat despite a five percent two-party swing, turning the historically safe seat of Davenport in to a two-party marginal seat for the first time. ABC psephologist Antony Green described it as "another poor result for the South Australian Liberal Party", following the 2014 Fisher by-election which saw Labor go from minority to majority government. Upper house casual vacancies Following the parliamentary resignation of former Labor Minister Bernard Finnigan on 12 November 2015 following his conviction for accessing child pornography. SDA secretary Peter Malinauskas filled the Legislative Council casual vacancy in a joint sitting of the Parliament of South Australia on 1 December. Following the parliamentary resignation of Labor MLC Gerry Kandelaars on 17 February 2017, Justin Hanson filled the Legislative Council casual vacancy in a joint sitting of the Parliament of South Australia on 28 February. Dates The key dates for the 2018 election were: 17 February 2018 Issue of the writs by the Governor of South Australia 23 February 2018 Close of rolls (noon) 23 February 2018 Close of nominations for party-endorsed candidates (5pm) 26 February 2018 Close of nominations for independent candidates (noon) 26 February 2018 Declaration of candidates and draws for ballot paper order (House of Assembly) 27 February 2018 Declaration of candidates and draws for ballot paper order (Legislative Council) 5 March 2018 Pre-poll voting opens 17 March 2018 election day (8am–6pm) 24 March 2018 last day to receive postal votes 26–30 March 2018 Expected formal declaration of results for House of Assembly seats in this week Mid April 2018 Expected formal declaration of results for Legislative council The last state election was