Prime Minister Turnbull has a number of triggers and potential triggers should he opt for a double dissolution election. If the Prime Minister decides to call a double dissolution election prior to the Budget (10 May), both Houses of Parliament would need to be dissolved, and the writs issued no later than Monday 4 April, for an election on Saturday 7 May.
Implications for senators' terms of office
The major effect of a double dissolution election is that the entire Senate is dissolved, meaning that all Senate positions are up for election. The past nine general elections (from 1990 onwards) have been for the House of Representatives and half the Senate. Since Federation there have only been six double dissolution elections, with the last in July 1987.
If the Senate is dissolved, when the new Senate meets following the election section 13 of the Australian Constitution requires the Senate to divide senators for each state into two classes: those having three-year terms, and those having six-year terms. Under section 13 also the two classes must be as nearly equal in number as practicable. One purpose of the shorter three-year term is to restore the rotation of the Senate, which occurs at half-Senate elections.
The Constitution does not prescribe the mechanism for the division of senators into the two classes—the Senate is free to adopt any criteria it chooses. To date, division into the two classes has been based on the number of votes received at the election (which determines the order of election), with those elected first becoming senators with six-year terms and those elected last becoming senators with three-year terms.
While other mechanisms have been canvassed, they have not been implemented. An amendment to the Commonwealth Electoral Act 1918 (‘the Act’) introduced after a 1983 Joint Select Committee on Electoral Reform proposal provides for a recount of Senate votes to determine the order of election after a double dissolution. Under section 282 of the Act, the recount uses a half-Senate quota (14.3%), rather than a full-Senate quota (7.7%), and excludes unsuccessful candidates from consideration.
However, the Senate is not bound to use section 282, and may decide the means of dividing senators into the two classes of term by resolution. This occurred after the last double dissolution election in 1987 when the Senate voted on 17 September 1987 to use the method outlined above (the number of votes received at election).
On 29 June 1998, the Senate agreed to a motion by the then Leader of the Opposition in the Senate, Senator John Faulkner, indicating support for the use of section 282 in a future division of the Senate. Senator Faulkner expressed the Opposition’s view that a decision to adopt the section 282 recount method should be made prior to any double dissolution election, and that the section 282 method was the fairest mechanism for dividing senators into the two classes. However, it was pointed out by Senator Bob Brown that the Senate could change the mechanism in the future. On 22 June 2010 the Senate agreed to an identical motion by the then Shadow Special Minister of State, Senator Michael Ronaldson, without debate.
Implications for future elections
Under section 13 of the Constitution the terms of senators elected at a double dissolution election are deemed to have commenced on 1 July preceding the date of the election, and the next election to fill vacant Senate places must be held in the year before they become vacant. Thus if a double dissolution election was held on Saturday 7 May 2016, elected senators’ terms would be backdated to 1 July 2015, and a half-Senate election would need to be held before 30 June 2018.
In addition, in order to reintroduce simultaneous House of Representatives and half-Senate elections (the norm now for 25 years), a House of Representatives election would need to be held at the same time as the 2018 half-Senate election. This would shorten the term of the House of Representatives by about a year to just two years.