What is a double-dissolution election?
A double dissolution is when the governor general – usually on the advice of the prime minister – dissolves both houses of parliament in preparation for an election. Senators are elected for six years, whereas MPs have a three-year term, so in normal elections only half the Senate faces the voters. The other half stay on regardless of who is elected in the House of Representatives. The drafters of the constitution thought this would offer a degree of continuity in the governance of the country. In a double dissolution, all Senate spots are up for grabs.
Why have one?
Double-dissolution elections are called when there is a deadlock over the passage of legislation. Governments are formed by having a majority of seats in the lower house, but often do not have a majority in the Senate, so deadlocks arise frequently. Double dissolutions effectively put the fate of the contested legislation in the hands of the voters.
After a DD election, there is a joint sitting of both houses so that the newly elected MPs and senators can vote to resolve the legislation.
Do we have grounds for a double dissolution now?
Yes. The government can call a double dissolution if legislation has been rejected by, or failed to pass, the Senate twice, with a gap of at least three months after the first rejection.
The government currently has two triggers for a double dissolution – that is, two pieces of legislation that have been rejected twice by the Senate: the scrapping of the Clean Energy Finance Corporation (CEFC) and the toughening of union governance through the registered organisations bill.
On Monday the prime minister, Malcolm Turnbull, warned the Senate that if it did not pass legislation relating to the re-establishment of the Australian Building and Construction Commission, which has been rejected once by the Senate, and the registered organisations bill, he would call a double-dissolution election.
Turnbull ruled out using the CEFC as an election trigger, focusing instead on the two industrial relations bills.
What does that mean for the timing of the election?
A double dissolution must be called not less than six months before the House of Representatives’ three-year term expires. That doesn’t give the government much time – it must call a double dissolution by 11 May.
Turnbull said he would go to a double-dissolution election on 2 July if those bills were not passed. In practice, voters will not have to go to the polls much earlier than they would have anyway, as the earliest a government could go to a normal half-Senate election is 6 August. The latest they could go to the polls is in January, but governments have historically avoided Christmas election campaigns, as they struggle to get their message to voters during the festive season.
What does it mean for senators?
Vacating the Senate means voters in the states must elect 12 senators instead of the usual six elected in a half-Senate poll. Senators need to get to the threshold of one-thirteenth of the votes in their state to be elected.
(The Australian Capital Territory and Northern Territory have only two senators each, elected every three years alongside the House of Representatives.)
In a double dissolution the number of senators up for election is doubled, so the threshold for election is halved. That could mean that more crossbench senators are elected, reducing the potential for the government to hold a majority in the upper house.
This makes the Senate voting changes passed last week even more crucial. These changes limit the ability of minor parties and independents to get elected by letting voters, rather than parties, dictate preference flows.
Only one member of the crossbench (John Madigan) was up for re-election this year – the remaining seven crossbench senators face the prospect of going to the voters much sooner than they would have otherwise needed to.
How risky is it to call a double dissolution?
Potentially very risky. There have been six such elections since federation, and in two of them the party that was in government lost its majority after the poll.
• This article was amended on 22 March 2016 to correct the proportion of the vote senators need to get from one-twelfth to one-thirteenth.
