Illustration: Andrew Dyson. For supporters of the "Yes" campaign, there are two main options. First and most preferred, there is the option of a successful vote on a same-sex marriage bill in the Federal Parliament. Three bills on marriage equality have come before Parliament to date and none have passed, but events in Ireland must surely be weighing heavily on wavering MPs Peak body Australians for Marriage Equality believes at least 72 lower house MPs would now vote for same-sex marriage, which is just four votes shy of the 76 required to pass a bill. In the Senate, AME estimates same-sex marriage has 39 supporters and so would pass with a majority of one. Unfortunately, the organisation's assessment of the numbers in Parliament appear overly optimistic. Internal number crunchers on both sides continue to believe a vote on same sex-marriage is unlikely to succeed in the 44th Parliament.

These insiders are more cautious in counting the votes of members who are yet to publicly declare their support, and believe the Senate has significantly more socially conservative Senators than AME's count suggests. On Sunday, Prime Minister Tony Abbott did not give any new ground on the question of Liberal MPs having a conscience vote. With a Liberal leadership challenge still possible, neither the PM nor any of his rivals will dare antagonise the conservative block of the party room. We remain incapable of a reform achieved by about 20 other democracies, including now the strongly Catholic nation of Ireland.

So the PM's formulation of words on the issue remains that the party room can decide what policy it takes to the next election, but cannot change its position from the last election, nor allow a conscience vote, in the current term. If this remains the position, then marriage equality is still years away in Australia. (Remember, senators are elected for six-year terms.) Against this backdrop, a second option of a plebiscite, as distinct from a referendum, must surely be considered by advocates for change. Abbott ruled out a referendum at a press conference on Sunday, because referendums are only required for a proposal to change the constitution. This is correct. Unlike Ireland, Australia's constitution does not limit the power of the Parliament to pass a law in favour of same-sex marriage. This was confirmed by the Australian High Court in 2013 in the ACT same-sex marriage case.

However, a plebiscite of the Australian people could be used by the government to decide a national question that does not affect the constitution. It could be used to test whether there is sufficient support for same-sex marriage, and provide a means of circumventing the intransigence of the Parliament. AME remains opposed to the suggestion of a public vote as a diversion and a delaying tactic. But this stance is based on the optimistic view that the numbers in Parliament are very close. Eminent constitutional scholar George Williams has also dismissed the plebiscite idea as a $100 million opinion poll that would be publicly divisive and still needs to get the approval of Parliament. This view fails to grasp the truly historic events in Ireland in recent days, with a vote that attracted the highest voter turnout since 1937, was spearheaded by young people, and has shown politics can still occasionally deliver pure joy to the vast majority of the people. Speaking after the result, the Catholic Archbishop of Dublin, Diarmuid Martin, reflected the decency of the Irish people as a voice for harmony, and progress.

"I think the church needs to do a reality check right across the board ... have we drifted away completely from young people?" he said. The Irish vote was also another endorsement for new democratic processes, with a citizen-based constitutional convention decisive in recommending the referendum in the life of the Parliament. A plebiscite in Australia might also provide a political fix for the Prime Minister. Opinion polls suggest a majority of Liberal voters now support marriage equality. (It should not be forgotten that conservative prime ministers in Britain and New Zealand have recently led their countries to marriage equality.) A national vote on this single issue would allow Liberal voters to express their discord with the party position, while still allowing them to vote Liberal in a general election. Of course, Parliament would still need to give approval to the plebiscite being held and the wording of the question. But for many parliamentarians, throwing this issue open to the Australian people would be easier to support than casting a vote on the issue itself.

If the vote was held at the time of the next election, it would allow the Liberal Party to move forward on the issue without directly breaching its promise at the last election. Nicholas Reece is a principal fellow at the University of Melbourne.