Tony Abbott has denied his party room a free vote on the issue of same-sex marriage, thereby dooming the cross-party bill on the matter introduced on Monday. Abbott has instead committed to holding either a plebiscite or a referendum on the issue sometime during the next government. Why would Abbott, a staunch opponent of same-sex marriage, put the issue to a vote of the people, when between 60 and 70% of Australians support it? And what’s the difference between a referendum and a plebiscite anyway?

What’s a referendum?

According to the ABC’s resident psephologist Antony Green, on his excellent blog explaining the difference, a referendum is a national vote to amend the Australian constitution. To achieve a “yes” result, a majority of the nation must vote “yes”, and a majority of people in at least four of the six states must also vote “yes” (although residents of the ACT and Northern Territory must vote in referendums, their votes only count towards the national total, not the “majority of states” equation). Because of this double majority requirement, it is much harder for a referendum to succeed than for a plebiscite to do so.

Of the 44 referendums so far held in Australia, just eight were carried. The most recent referendums to get the thumbs-up from the majority of the electorate and the majority in at least four states were the three 1977 referendums: to introduce a compulsory retirement age (70) for all federal judges; to allow voters in the ACT and NT to have their say in referendums; and to allow parties to fill casual Senate vacancies.

Five further referendums (in 1937, two in 1946, one in 1977 and one in 1984) achieved a majority vote but failed to clear the second hurdle of achieving a majority in at least four states.

Referendums are binding, so if they are carried they must be made law.

What’s a plebiscite then?

A plebiscite is similar to a referendum, but it does not need the second requirement; a plebiscite passes if a simple majority of voters in all states and territories vote “yes”. There is a catch though, and it’s a big one: plebiscites are not binding. They are a way for the government to take the electorate’s temperature on an issue, but the government does not have to abide by the result. A plebiscite can also be held on matters that don’t have to do with changing the constitution.

Marriage is not defined in the constitution, so why would we have a referendum on it?

Section 51 (xxi) of the Australian constitution enumerates the powers of Parliament and says:

“The Parliament shall, subject to this Constitution, have power to make laws for the peace, order, and good government of the Commonwealth with respect to … marriage.”

Amending the constitution would mean amending this section to restrict the laws Parliament could pass in relation to marriage, e.g. adding the phrase “provided that all laws apply equally to same-sex and opposite-sex marriages” or similar.

A referendum seems a very high bar, what about having a plebiscite?

It is likely same-sex marriage would pass in a plebiscite, but the rub is the government would not then have to accept the will of the people. In October 1916, the government asked Australians whether the government should introduce compulsory conscription in order to send more troops to World War I. The citizenry voted no.

In December 1917 Australia asked its citizens again whether it should introduce conscription. The measure was again defeated.

Australia introduced conscription in 1942 to provide troops for World War I. It did not put the issue to the people this time.

Says Green:

“It would be unlikely that changes to the Marriage Act would be dependent on the plebiscite. The Parliament would still have to legislate the changes and would presumably do so dependent on the plebiscite result.”

Is it possible the Abbott government is mucking around with plebiscites and referendums because it doesn’t actually want marriage equality?

We wouldn’t care to speculate.