As the first half-Senate election held after a double dissolution, the election on May 18 will fill vacancies for the 36 state seats to which the Senate itself allocated three-year rather than six-year terms, together with the four territory seats whose terms are tied to the House of Representatives. The major parties agreed the allocation should be done as it always had been, with reference to the candidates' order of election in the count, granting six-year terms to the first six elected out of 12 in each state. However, this method is flawed in that it can distort the proportionality of party representation, typically to the advantage of larger parties. For this reason, the Hawke government legislated to have the Australian Electoral Commission conduct follow-up counts after each double dissolution election to determine the six leading candidates by including only the 12 elected candidates in the count. However, the Senate is not bound by the result, and has chosen not to be on both the occasions where it has had an opportunity. Consequently, full terms that would have gone to Lee Rhiannon of the Greens in New South Wales and Derryn Hinch instead went to Deborah O'Neill of Labor and Scott Ryan of the Liberals.
The state of the cross-bench
The 2016 result left seven parties represented on the cross-bench, of whom the Greens remained dominant with nine seats, consisting of two apiece in Victoria, Western Australia and Tasmania, and one each in New South Wales, Queensland and South Australia. Of the others minor parties, the only genuinely national concern was Pauline Hanson's One Nation, who made a spectacular comeback to win four seats after having gone unrepresented since 2005. This included two seats in the party's home state of Queensland and one apiece in New South Wales and Western Australia. The other parties reflected locally dominant strains of anti-major party sentiment, by far the most successful being the Nick Xenophon Team, which won three seats in South Australia in addition to its lower house seat of Mayo.
Elsewhere, two candidates elected as minor party cross-benchers in 2013 won re-election, neither of whom represented the phenomenon of micro-party party preference harvesting. David Lejoynhelm of the Liberal Democrats won his New South Wales Senate seat in 2013 with 9.5% of the statewide vote, which related only to preference harvesting to the extent that it encouraged a proliferation of parties and thus an enormous ballot paper. The Liberal Democrats had the good fortune to draw first position on the ballot paper, maximising the potential for them to be confused with the Liberal Party. With 12 seats per state up for election in 2013 and the new rules in force, Leyonhjelm was able to hold on with 3.1% of the statewide vote. In Tasmania, Jacquie Lambie had been elected in 2013 as part of the well-funded juggernaut of Clive Palmer's Palmer United Party, which scored 6.6% statewide, then won off her own bat after in 2016 after establishing herself as a local folk hero in her three years as a Senator.
The changing face of the Australian Senate, 2016-19
The Coalition goes into the election with 31 seats in the Senate, a net gain of one on the 2016 election result, following one loss and two gains. The loss came in February 2017 when Cory Bernardi quit the Liberal Party to found Australian Conservatives, depiving it of a full-term seat in South Australia. This was balanced one year later when independent Senator Lucy Gichuhi joined the Liberal Party. Gichuhi came to parliament in April 2017 after the High Court ruled disqualified South Australian Family First Senator Bob Day due to a pecuniary interest with the Commonwealth, in an early foretaste of the looming Section 44 eligibility crisis. The court declared a recount should be conducted with Day excluded, causing the Kenyan-born Gichuhi to be elected from second position on the Family First ticket. Shortly afterwards, Gichuhi declined to follow Family First into its merger with Australian Conservatives, and sat for nearly a year as an independent before joining the Liberal Party.
The subsequent parliamentary crisis arising from dual citizenships had a marked effect on the Senate, leading to the resignation or disqualification of seven of its members: two from the Greens (Scott Ludlam from Western Australia, serving a long term, and Larissa Waters from Queensland, serving a short term), one each from the Liberals (Stephen Parry from Tasmania, short term), the Nationals (Fiona Nash from New South Wales, long term), Labor (Katy Gallagher from the Australian Capital Territory), One Nation (Malcolm Roberts from Queensland, short term), the Nick Xenophon Team (Skye Kakoschke-Moore from South Australia, short term) and Jacqui Lambie (Tasmania, long term). As had been the case after Bob Day's disqualification, each vacancy was filled by a recount that elected the next candidate along on the relevant party's ticket from 2016. The only case that directly disturbed party representation was Fiona Nash of the Nationals, who was replaced by Jim Molan, a Liberal. Larissa Waters returned to the Senate last December after her successor, Andrew Bartlett, agreed to make way for her.
A further three changes of party representation have arisen indirectly from the Section 44 crisis, including the second of the two seats gained since the election. This arose when Jacqui Lambie was replaced in February 2018 by her running mate from the election, Steve Martin. Lambie expected Martin to resign so she could fill his vacancy after sorting out her citizenship issues, but Martin refused. He was promptly expelled by her party, the Jacqui Lambie Network, and joined the Nationals the following May. The Nick Xenophon Team, which in April 2018 renamed itself the Centre Alliance, lost one of its three seats in February 2018 when the recount to replace Skye Kakoschke-Moore gave the seat to Tim Storer, who had already quit the party the previous November and would sit as an independent. One of the two seats lost by One Nation was that of Malcolm Roberts, whose successor, Fraser Anning, quit the party on the day he was sworn into the Senate in November 2017. The other is the New South Wales Senate seat held by Brian Burston, who quit the party and joined Clive Palmer's United Australia Party in June last year.
The shadow of the 2016 electoral reforms
The election will be significant as the first half-Senate election to be conducted under the reformed electoral system that abolished group voting tickets, whereby the overwhelming majority of voters chose a single party above the line which determined the full order of their preferences. Introduced at the 1984 election to address the increasingly onerous task placed on voters of ranking each of an ever-increasing selection of Senate candidates, the system proved open to manipulation from “preference harvesting” by networks of small parties feeding each other's preferences, producing results as arbitrary as Ricky Muir's win for the Australian Motoring Enthusiasts Party in Victoria in 2013 from 0.5% of the statewide vote.
The introduction of this system at the 2016 election succeeded in preventing more obviously perverse results, but not in what was no doubt its secondary objective of reducing the size of the cross-bench, and with it the difficulties of governments in enacting legislation. This was a result partly of the ongoing decline in the major parties' share of the vote, which collectively fell to less than two-thirds of the total, and partly of the extraordinary fact of it being a double dissolution election, reducing the quota for election from 14.3% to 7.7%. The result was that representation of non-major parties rose still further, from 23 seats out of 76 after the 2013 election to 25. The application of the new system at an election with the higher quota will make life more difficult for smaller parties, but recent history suggests One Nation will be competitive or better in their strongest states, and locally popular players such as Derryn Hinch in Victoria and Jacquie Lambie in Tasmania also have a good chance of achieving the required mass of support.