This week’s Parliamentary sittings couldn’t come soon enough for Malcolm Turnbull. Last night’s split on the Government’s infrastructure bill capped off what turned out to be a shocker of a week.

Yesterday Turnbull and the Prime Minister missed Question Time to attend the funeral of Afghanistan casualty Lieutenant Fussell. Gillard and Bishop stepped in. While Bishop looked more comfortable than during her enforced silence in Question Times earlier this week, the difference between Government and Opposition was stark. One side has a deputy who looks every inch ready for the top job, the other does not, and both sides know it.

Despite pressure from those noted Labor fans at The Oz, Bishop’s not going anywhere for the time being. Her fate is in her hands, whether clawed or not.

The Nats also left the reservation not once but twice this week, over carbon sinks and infrastructure. Fiona Nash took a bullet for crossing the floor, resigning from her shadow Parliamentary Secretaryship. There was criticism of Turnbull for letting her go, but it was the right decision — you can’t cross the floor on an issue in your own portfolio, which Nash did. But as one of the few sane and intelligent Nats, Nash will be missed, including by her shadow Minister, Greg Hunt. The party leadership should think seriously about replacing her with South Australia’s Simon Birmingham, even though he’s a Liberal. Birmingham’s a great young talent and an effective communicator who has been closely engaged with water issues.

This should be put into some context: in opposition it matters less if you cross the floor on the Government’s bills, and particularly so when the result is a foregone conclusion. Even so, the seemingly regular departures of the Nats confirm that making Barnaby Joyce Senate leader has, rather than curtailing his own tendency to wander, merely allowed him to take some others with him. In that context, the new tendency of strict Coalitionist Ron Boswell to cross the floor is a potentially worrying sign.

Meanwhile, the joint party room has started getting itself into a lather over asylum seekers again. There’s another split, this time within the Liberals, over detention. Petro Georgiou and WA Senator Alan Eggleston are both on the Senate-Reps Migration Committee and joined new Greens senator Sarah Hanson-Young in a dissenting report from the current inquiry into immigration detention. In particular, they recommended detainees be held for no longer than 30 days before coming before a court. The report prompted a number of Coalition MPs to voice their strong support for the Howard Government’s approach to mandatory detention. Turnbull endorsed their views, on the same day he promised “innovative” new Liberal Party policies.

The only positive headlines Turnbull managed this week were for a stunt connecting the States’ difficulties raising credit with a possible Middle East investment delegation next year. Wayne Swan was casually dismissive of the idea of an infrastructure bank yesterday and the issue dropped from view, overtaken by end-of-year shenanigans.

It wasn’t supposed to be like this for Turnbull, trailing badly in the polls despite the economic crisis, with a divided party, shadow Cabinet ministers skipping votes, the Nationals demonstrating their independence and mandatory detention looming as a divisive issue inside and outside the party. Turnbull was supposed to take the fight to the Government with his customary vim and vigour, locking MPs in behind him by giving them the chance of victory in 2010 that they never had under Nelson, and getting the Coalition to a competitive poll position. The hope might have been that the Coalition would go into the summer break with a spring in its step and the hope — not that it would ever have been articulated in this way — that rising unemployment would further undermine the Government’s position in 2009.

That might yet happen but for now the summer break will mainly be an opportunity for Turnbull to worry about his shadow Treasurer and wonder which issue the Nats — none of whom are particularly fond of the former investment banker who leads them — will break on next.

During the week Kevin Rudd was trying to play up the threat to Turnbull posed by Peter Costello. That’s a long way off, and Costello could pull the pin at any moment and walk if he finds a job that suits him. But if the Turnbull experiment fails in 2009, those of us blessed with 20-20 hindsight will identify this week as where things started to go wrong.