Election explainer: what does it mean that we're having a double-dissolution election?

Malcolm Turnbull has made the journey to Government House at Yarralumla to ask the governor-general to dissolve both houses of parliament and hold a double-dissolution election.

Both the Senate and House of Representatives will be dissolved. The writs will be issued, causing the election to be held.

Section 5 of the Constitution requires the governor-general to issue the writ for the House of Representatives election. Section 12 of the Constitution requires the state governors to issue the writs for the election of the senators in each state.

While the writs will formally set out the timeline for the election process, we already know the key detail: a double-dissolution election, to be held on July 2.

Double-dissolution elections do not come along very often. This election will be only the seventh double-dissolution election since federation. The last double-dissolution election was held in 1987, when the Hawke government was returned to power.

Double-dissolution elections do not always go the way of the incumbent government. In three of the six previous double-dissolution elections – in 1914, 1975 and 1983 – the government was defeated.

So, what is a double-dissolution election? How does it differ from an ordinary election? And why the rush after the budget?

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.

After a double-dissolution election, the rotation for Senate elections needs to be re-established. This means that half the senators will serve a “long term” and half will serve a “short term”. Only the “short-term” senators will be up for re-election at the next half-Senate election.

The process for determining which senators serve a “short term” is complicated.

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. The two bills that would reinstate the Australian Building and Construction Commission (ABCC) – which the Senate rejected for a second time in April this year – and the Registered Organisations bill are being used as the “trigger” for the July 2 election.

After a double-dissolution election, if the Senate again rejects the same bill, 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.

There has only been one joint sitting of parliament – in 1974.

While the Constitution provides a procedure for resolving these deadlocks, it does not require the government to put the proposed trigger legislation (in this case, the ABCC bills and Registered Organisations bill) before the next parliament.

There is some suggestion that at 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 after the budget?

The timeline for a double-dissolution was 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.

This is why the budget was moved forward to May 3. It allowed sufficient time for Opposition Leader Bill Shorten’s budget reply speech, and for parliament to pass supply, before an election is called and parliament is dissolved.

The government now enters “caretaker mode”. Candidates and voters alike are bracing themselves for an eight-week election campaign.