Explainer: what are double-dissolution elections? And why might we soon have one?

Prime Minister Malcolm Turnbull on Monday laid down an ultimatum to the Senate: pass the government’s industrial relations legislation or face a double-dissolution election.

The Senate will sit from April 18 to consider two bills that would reinstate the Australian Building and Construction Commission (ABCC), and the Registered Organisations bill, which would establish a body to provide greater investigatory and information-gathering powers over unions.

Turnbull also announced the budget will be handed down a week early, on May 3. This move clears the way for a double-dissolution election.

So, what is a double-dissolution election? How does it differ from an ordinary election? And why is timing so important?

What’s the difference?

In an ordinary election, all seats in the House of Representatives – but only half the seats in the Senate – are up for grabs.

Senators are elected for a six-year term. Half are up for re-election every three years.

But, in a double-dissolution election, there is a full, rather than the usual half, Senate election. All 76 Senate seats are vacated.

What is a double-dissolution election?

Section 57 of the Constitution sets out a mechanism for resolving disputes between the two houses of parliament that arise when the government cannot get its legislation through the Senate.

If a bill has passed the House of Representatives but the Senate either fails to pass or rejects it on two occasions – with a period of at least three months between each attempt – the government can request the governor-general dissolve both houses of parliament and a double-dissolution election be held.

A bill failing to pass or being rejected twice by the Senate is sometimes said to be a “trigger” for a double-dissolution election.

After a double-dissolution election, if the same bill is again rejected by the Senate, the government can ask the governor-general to convene a joint sitting of the House of Representatives and the Senate. Because the government will usually have a majority in the lower house – and there are twice as many lower house MPs as there are senators – a joint sitting is more likely to pass the legislation.

While the Constitution provides a procedure for resolving these deadlocks, there is no requirement for the government to put the proposed trigger legislation before the new parliament.

There is some suggestion that if the government proceeds to a double-dissolution election, the new Senate electoral system might return the government a Senate majority. If that were the case, a joint sitting of both houses would be unnecessary – the government could expect that its legislation would pass both houses.

However, there is a further complication in a double-dissolution election. Double the number of Senate seats up for grabs also means the “quota” of votes required for a Senate seat is reduced. This makes it easier for minor players to win a seat.

Why the rush?

The government already has two bills that have twice been rejected by the Senate and would provide triggers for a double-dissolution election: the abolition of the Clean Energy Finance Corporation, and the Registered Organisations bill.

The Registered Organisations bill is set to be put before the Senate for a third time. However, on this occasion, the Senate has forewarning that if it blocks the bill again, the government will call a double dissolution.

If the Senate was to pass the ABCC bills and the Registered Organisations bill, the government could technically still trigger a double-dissolution election using the Clean Energy Finance Corporation bill.

The timeline for a double dissolution is rather tight. This is because Section 57 requires a double-dissolution election cannot take place in the final six months prior to:

… the date of expiry of the House of Representatives by effluxion of time.

This means that, as the House of Representatives first sat after the last election on November 12, 2013, the house’s three-year term expires on November 11, 2016. The last day on which a double-dissolution election could be called is May 11, 2016.

The budget has thus been moved forward to May 3 to allow the parliament sufficient time to pass it before an election is called and parliament is dissolved.

Why is the Senate coming back in April?

Because of this tight timeline, Turnbull’s first issue was to get senators back to Canberra to consider the proposed legislation. The current session of parliament was not scheduled to sit again until the budget on May 10.

Last week, the Senate passed a resolution that it would not sit again before May 10 without the agreement of a majority of senators. This would have left the Senate with no time to debate and vote on the ABCC bills and the Registered Organisations bill as well as passing the budget.

However, the government has managed to sidestep this problem by asking the governor-general to terminate (or “prorogue”) the current session of parliament and recall the parliament for a new session to sit from April 18, 2016.

By terminating the current session, the government avoids any problems associated with trying to reschedule the current session. While proroguing parliament terminates any business before the parliament, the Senate’s standing orders allow that these matters of business can be reintroduced and the bills before the Senate can be restored.

After many weeks of speculation, the government has laid down the challenge for the Senate and smoothed the path for a double-dissolution election.