If you were aboard the Titanic as the third officer and you knew what was about to happen, and that sinking was inevitable, why would you want to take over the captaincy of the ship? That appears to be the incredible situation in which Tasmanian Labor minister David O’Byrne has placed himself as speculation mounts that he will seek to overthrow Premier Lara Giddings.

Labor is in a coalition government with the Greens. It has 10 seats in the 25-seat House of Assembly. So do the Liberals, led by Will Hodgman, son of Michael. The Greens have the other five.

The polls show that Labor stands to win even fewer seats in the next election, not due until 2014. It has 23% support to the Liberals’ 54% and the Greens’ 20%. Giddings is polling at 19% as preferred leader, only 2% above Paul Lennon when he pulled the pin.

So Tasmanian Labor’s major challenge at the moment is to prevent the Greens becoming the official opposition party at the next election and Labor running a distant third.

Why, if this sinking is inevitable, would third officer O’Byrne want to take over the wheel? Would it not be better for Giddings to go down with the ship, leaving O’Byrne free to launch a new model after the next election?

After The Mercury in Hobart yesterday splashed with a story that O’Byrne was mounting a challenge, Giddings took the extraordinary step of calling a press conference to say that she had spoken to him and that he had denied it. I would have thought the appropriate course of action would have been for her to stay in the background but demand that he issue a denial. Failing that, she should sack him or bring on a spill next week.

Today The Mercury identified the motley crew of six who are said to support O’Byrne. One of them is his sister. The others are at the shallow end of the talent pool. The wiser heads are backing Giddings.

There are two other forces at play here. Public sector unions are incensed that Giddings, who is also Treasurer, is taking the knife to government jobs to preserve the budget. Union bosses figure that if they get rid of Giddings and replace her with O’Byrne, a former union boss himself, then they’ll get more sympathetic treatment. That doesn’t necessarily follow. In Tasmania, Treasury tends to call the shots in the budget, no matter who’s Treasurer.

Tasmanian business backs Giddings. They approve of what she is doing with the budget. She thinks the same way as they do.

O’Byrne has to be careful the way he plays this. Yesterday he refused to rule out a challenge, using the usual spin about being a team player.

Already he is seen as being disloyal to Giddings and the electorate at large would not forgive him for disloyalty, especially one particular sector of the electorate. Giddings is Tasmania’s first woman premier.

Far better, one would have thought, for third officer O’Byrne to stay on the bridge and help minimise the damage to the crew and passengers when the inevitable happens in 2014.