Labor's decision to kill off the same-sex marriage plebiscite has delayed the reform indefinitely.

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.