OPINION: As sure as night follows day, government defeats in the Senate lead to suggestions of a double dissolution. Prime Minister Tony Abbott has fuelled this by saying such an election may be held in six to 12 months if the Senate does not fall into line.

A double dissolution means an early election at which all members of the House of Representatives and Senate are elected, as opposed to a normal election at which only half the Senate is chosen. It offers the only means of cutting short the six-year terms of the micro-party Senators chosen at the last election.

A prime minister can call a double dissolution under section 57 of the Constitution when there is a deadlock between the House of Representatives and the Senate. The Senate must fail to pass a bill that has gone through the House of Representatives, and this must occur again after three months have elapsed.

When this happens, the government gains a trigger to call an early election. Such polls are often threatened, but rarely held. Australia has had double dissolution elections only six times, the most recent being more than a quarter of a century ago. They were in 1914, 1951, 1974, 1975, 1983 and 1987.

Given this record, the smart money would be on Parliament running its full term. If nothing else, there is no political upside to Abbott calling an early election unless he has strong prospects of winning, and the polls do not suggest this.

A double dissolution may also amplify his problems with the Senate. Electing the whole of the Senate in one go means the quota to win a seat is almost halved, from 14.3 per cent to 7.7 per cent. A lower quota, with the prospect of more micro party senators, is hardly desirable for a Prime Minister wanting a more pliable upper house.

Nevertheless, the prospect of a double dissolution election cannot be written off. It can still offer significant upsides to Abbott if approached in the right way.

First, such an election should not be called until Parliament has reformed the Senate voting process. It is widely recognised that this is broken, as micro parties can game the system to produce a lottery-like effect by which a candidate with an infinitesimal number of first preference votes can win a seat.

Parliament’s joint standing committee on electoral matters recently reached a consensus on how this should be fixed. It recommends the system be changed so people can indicate their preferences both above and below the line on the Senate voting ticket.

This means voters, and not parties, control the flow of preferences. A double dissolution election held under these rules can advantage those parties and candidates that attract a significant number of votes. Micro parties with little support will not be elected.

Second, a double dissolution can be held close to the time of the next federal election. This allows the government to run almost to full term and lessen the political downsides.

The constitution says a double dissolution cannot take place within six months of the expiry of the House of Representatives. With it due to expire on November 11, 2016, a double dissolution election needs to be called by May 11, 2016. The result may be a mid-2016 double dissolution election, rather than a normal general election a few months later.

Third, a double dissolution may offer the only means for the government to pass some of its more contentious policies. This is because the procedure also provides a special way to enact disputed legislation.

If the deadlocked bills are still not passed after a double dissolution election, a re-elected Prime Minister can call a joint sitting of Parliament at which both houses vote collectively on the bills. As the constitution requires the House of Representatives to be twice the size of the Senate, a government can win such a vote when its lower house majority offsets its deficit in the Senate.

Only one double dissolution has been followed by a joint sitting. That was in 1974 when the Whitlam government used the procedure to enact reforms including Medibank (now Medicare) and one-vote, one-value in the allocation of voters to electoral districts. A double dissolution may be the only viable means for Abbott to bring about changes such as those to higher education and a GP co-payment.

People should be sceptical about Australia heading to an early double dissolution election. However, it is a more likely prospect if it is held near the end of this term of Parliament and in a way that prevents more micro party senators from being elected. It can also offer Abbott an historic opportunity to enact major reforms that may otherwise never be passed by the Senate.

George Williams is Anthony Mason Professor of Law at UNSW.

This opinion piece was first published in the Sydney Morning Herald.