There have been some ineffectual federal opposition leaders in our recent political history, with the Liberals’ Alexander Downer and Brendan Nelson being two that most readily spring to mind.

Even John Howard, before going on to become Australia’s second-longest serving prime minister, had two attempts at being opposition leader before getting it right. On the other side of the political fence, the affable but prolix Kim Beazley also had two stints as opposition leader, but ultimately was not up to one of the toughest jobs in Australian politics.

Now voters are beginning to wonder if the latest Labor Leader, Bill Shorten, is up to the task. Following on from his appearance at the union royal commission, and the revelations divulged thereShorten has taken a battering in the opinion polls. According to one poll so far, the Government is also closing the gap between itself and Labor.

Depending on who you believe, the Opposition Leader’s colleagues may also be fast coming to the conclusion that they’re on a loser with Shorten.

Yesterday’s leak to the tabloid media of a confidential shadow cabinet discussion paper on policy options for reducing carbon emissions was particularly damaging for Shorten. Partly because it gave Tony Abbott the opportunity to dust off his great big tax scare campaign, but also because the leak represents the first crack in the united front that Labor has judiciously presented to voters since the conclusion of the Rudd-Gillard wars.

That is unless the document became public by accident, as some media outlets have helpfully speculated since the leak first became known.

While it is always wise to consider the possibility of a cock-up before suspecting a conspiracy, the timing of the exposé points to the latter.

Labor’s factions are manoeuvring behind the scenes in preparation for battle at next week’s national conference, which will include efforts to add ambitious emissions reduction goals to the binding party platform. Leaking the discussion paper may have been an attempt to raise the heat on the issue, thereby inciting enough public anger to dissuade those angling for the party to adopt tougher climate initiatives before the next federal election.

Whatever the motivation for the leak, the former Gillard government minister responsible for climate action, Greg Combet, who is currently advising his Victorian colleague Bill Shorten on climate policy, pointedly warned Labor MPs about political instability through a media interview last night.

When asked whether the leak was due to Labor infighting, Combet replied: “Well I hope that people have learnt the lessons of the Rudd-Gillard period and they’re not about to repeat it.”

Combet has become a regular feature on our screens in past weeks. First he was sitting with Shorten’s legal team when the Labor Leader attended the royal commission, and then yesterday he was doing media interviews in an attempt to hose down any public concerns about a carbon tax by explaining the difference between it and an emissions trading scheme.

It’s telling that Shorten, who is from Labor’s right, felt it necessary to wheel out the former minister to do so, when he has a perfectly serviceable shadow minister for climate change, Mark Butler, who incidentally also happens to be the new ALP President and a member of Labor’s left.

In another example of the dark synchronicity that currently seems to plague the Opposition Leader, the discussion paper leak sucked the oxygen away from Labor’s attempts to ignite its own great big tax campaign over the GST.

As a result, the speech delivered yesterday by Treasurer Joe Hockey to soften up state and territory leaders on the need for GST reform before they convened for next week’s retreat, was mostly given a clear run in the media. It took a unilateral and categorical no from Victorian Labor Premier Daniel Andrews to put Labor back into the debate.

Meanwhile, Shorten visited a school with Labor Senator Jan McClucas, who recently fell out of favour with her left faction and was dis-endorsed, as well as the candidate for Herbert, Cathy O’Toole. Shorten was clearly trying to score voter brownie points on education, which is a Labor strength, but was wrong-footed by the leak and out-gunned by Hockey.

Just as PM Abbott faced a number of pivotal tests of his leadership earlier this year, Shorten too has to survive a number of crunch points. One was his appearance last week at the union royal commission, another is to navigate next week’s national conference, and a third is to manage the aftermath of both events.

It may be enough for the Labor Leader to put in a pedestrian but competent showing. But if there is anything the leak of the climate policy paper suggests, it’s that some of Shorten’s colleagues are not yet prepared to give up the next election. If Labor’s opinion poll rating starts to dip lower than the Coalition’s (on a two-party preferred basis), their election-saving efforts will be considerable – and may need to include tapping Shorten on the shoulder to orchestrate an orderly transition to a new Labor leader.