Illustration: Andrew Dyson Which is why Labor wanted to know if Turnbull would force MPs from the Christian Right to back same-sex marriage if the public voted for change. Conversely, would they be accommodated, leading to the laughable situation of the public voting yes, and Parliament still voting no. Labor probably expected the Prime Minister to hedge, in a nod to internal doubters. Instead, he surprised by skipping straight past the problem of a post-plebiscite parliamentary vote, and it soon became clear why. Turnbull's elegant solution is to literally observe the terms of the July party-room compromise. His message? It was a plebiscite you demanded, so it is a plebiscite you shall have. Moreover, it will not simply be the general principle of marriage equality that is put to the people for a yes/no response, but the actual amendment to the Marriage Act in full. People attending the polling places will know exactly what they're voting on and, importantly, that it will be their votes that decide the issue. The Queensland Liberal-National Party MP Warren Entsch explained the new plan's neat logic. Parliament would be asked to do no more than pass contingent legislation during this term, setting out the amendment to be later endorsed or rejected, and the time-table for the plebiscite. Assuming an election some time around September or October 2016, that would see a public vote on this question put either later in 2016, or, more likely early 2017.

Illustration: Simon Letch The burly knock-about Entsch may be an unlikely champion of this issue but his reasoning stacks up against the stated rationale of the party room in July, when the public vote was endorsed. That rationale had three main elements: Cathy McGowan (right) with Liberal Warren Entsch and the Greens Sarah Hanson-Young after Mr Entsch introduced a private member's bill on marriage equality last August. Credit:Andrew Meares First, that the definition of marriage as set out in the act would remain explicit Liberal Party policy until the next election, beyond which it would become a matter of conscience. This was justified on the grounds that voters had elected the Coalition in 2013 with the orthodox definition of marriage stated in its platform.

Second, after the election the question of change or otherwise would be put to a plebiscite. Third, said plebiscite would be held later – next term – some time. It was a clear case of kicking the can down the road. To the "not now, not ever" camp, it even felt like a win. To them, the dangerous popular momentum towards change had been slowed, and the prospect of reform pushed over the horizon, where with a little luck and the right (Right) leadership, it would remain. After all, Abbott may have invited Entsch to form a cross-party grouping to draft a private members bill, but he had then revealed privately to colleagues that he would never allow Entsch's endeavours to come to a vote. Entsch and other Liberals had every right to have felt deceived. But now all of that has changed. With Abbott gone, Turnbull can simultaneously observe the precise terms of the Coalition party room formula, while progressing the issue towards conclusion.

After all, even many of the staunchest opponents of change in the party room – senators Cory Bernardi, Matt Canavan, Concetta Fierravanti-Wells and Zed Seselja – had promised to honour the plebiscite's outcome whichever way it went. None of which has stopped some arch-conservatives from crying foul, however. Dumped minister Eric Abetz came out swinging on Thursday, branding the Entsch model "a thought bubble and an ambush to boot". "Clearly it would be a breach of promise to the Australian people with the 2013 federal election, and it would not be taking into account the very strong view of the party room, so for Mr Entsch to simply drop this out there ... I don't think is a clever tactic, a fair tactic, or a reasonable approach," he said. Abetz and others also claim it would be unconstitutional as it would be an attempt by one parliament to bind a subsequent one. But constitutional law expert Anne Twomey believes it is possible, simply by writing into the amendment a condition stating that a new definition of marriage would only come into operation, once endorsed by a plebiscite.

Don't expect conservatives to accept that, though. The same people who, just weeks ago, were lecturing others about the higher virtue of a direct public vote are increasingly frightened that it may now actually happen, and frankly, that wasn't part of the plan. Mark Kenny is Fairfax Media's chief political correspondent.