Malcolm Turnbull must cross the floor, and it's not about principle

MALCOLM Turnbull has something to think about. Does he stick with his original commitment to cross the floor and vote for the government's emissions trading scheme, guaranteeing that any ambitions he might have left to return to the Liberal leadership are dashed once and for all?

Or does he abstain from the vote in what would be a humiliating backdown?

It is not much of a choice.

It is hard to see Turnbull doing anything other than crossing the floor.

However, last week senior Liberals were urging Turnbull to abstain from the vote - some even came away from their discussions with the impression he would heed their words. No surprises with that misunderstanding. Joe Hockey came away from his pre-leadership ballot discussions with Turnbull late last year thinking Turnbull had agreed not to contest the ballot if the spill motion were successful.

How did it come to this for Turnbull? It certainly wasn't because he was looking to take a principled stand on the issue of an ETS, no matter how hard he might try to rewrite history.

People shouldn't forget that Turnbull previously said Australia should not enact an ETS before the Copenhagen conference. That position was put to one side because he feared Labor would politically tear the Coalition apart if it gave the government a double-dissolution trigger on climate change by blocking the ETS. Turnbull therefore wanted his party to vote in favour of the ETS when it came to a vote before Copenhagen.

Not a lot of principle in that.

Liberals pride themselves on their tolerance of MPs exercising their consciences and crossing the floor if they feel strongly about an issue. That is why Petro Georgiou did so on refugee issues. But Turnbull will cross the floor to legitimise what was a tactical wrong call to support Kevin Rudd's ETS late last year, thereby justifying his own political downfall.

Somebody should acquaint Turnbull with the words of John Maynard Keynes: "When the facts change, I change my mind. What do you do, sir?"

As humiliating as it might be for Turnbull to accept, the fact is the politics of the ETS have changed.

However, because he ramped up his rhetoric about the need to pass the ETS when he thought doing so would be politically advantageous, he will look a fool if he backs down now.

Turnbull is in a lose-lose situation all of his own making.