Same-sex marriage denied and everyone - not just Malcolm Turnbull - shares the blame

It means if Australia is to achieve marriage equality, it will not be via the admittedly imperfect way proposed, even though it was the only way forward this term.

It also means that Malcolm Turnbull, arguably the most socially progressive Liberal prime minister in his party's history, and an equality supporter, will probably not be the one to deliver it.

In a bizarre circumstance in which the leaders of all the major parties agree with a given reform and have a clear majority of the public behind them too, the nation's political machinery cannot deliver.

In a re-run of its epic failure on carbon pricing when the planets were similarly aligned in 2009, the political class has made the good the enemy of the great and thus shown its real absence of class.

More perversely, despite Labor-Greens purity, the political price for this dysfunction will almost certainly be billed to Turnbull.

All of his options all look bad from here. He is hemmed in by conservatives who threaten armageddon if he seeks compromise, and by proponents who demand their way or infamy.

Turnbull was the one who argued correctly in mid-2015 that the Abbott government should have held a free parliamentary vote before the 2016 election to avoid marriage becoming a distraction and a campaigning advantage for Labor.

He then abandoned that proposition in his deal with conservatives to replace Abbott agreeing instead to honour the latter's transparent can-kicking exercise of a holding public vote after that election.

Agree with it or not though, Turnbull stated his position, won the election, and then formed a government. He has endeavoured to act as promised. Yes, there is a danger of hate-speech. But surely the most egregious material slight against same-sex couples is enacted daily by the continuation of legal discrimination.

In Parliament on Wednesday, Turnbull observed that the Labor Party is not as interested in allowing gay couples to marry as it is in wringing every ounce of political capital from his failure.

Unfortunately for Turnbull, there is plenty of wringing to come. The PM has made clear that if the plebiscite goes down, he will not return to it this term. Internally, he would face a revolt if he tried.

But avoidance is no solution either because it means all he can do between now and then is promise another post-election plebiscite in 2019. Labor is demanding a free parliamentary vote - even though, bizarrely, its pro-change policy will soon be binding on Labor MPs. Go figure.

Turnbull was right to want this dealt with before 2016 in order to manage the politics. Now he is locked in to it festering right through to the next election.