More from Business Spectator on the rumoured behind the scenes ALP struggle over the carbon price: 
It may prove mere coincidence that the day Business Spectator breaks news of Shorten possibly maneuvering on carbon pricing, Combet declares removing it would be “immoral”, arguably his strongest line since the policy was enacted.Regardless, his doorstop interview makes for intriguing reading in light of the Shorten speculation.
Journalist: Is Labor still committed if you find yourself in Opposition come September to blocking any repeal of the carbon tax?
Combet: You bet. It is the right public policy position for this country... Labor has stood for it for a long time and we will stand for a long time.
Journalist: So do you reject Mr Abbott's remarks that the election will be a referendum on the carbon tax?
Combet: People will know what Labor's position is, I can assure you, in the lead up to the election and we will adhere to it and we intend on winning the election.
It’s hard to divert from this line to one post-election along the lines of ‘sorry, we were wrong, carbon pricing isn’t the way forward.’
If Shorten wants to distance Labor from the policy, it appears Combet won’t make it easy for him – which is no surprise given a retreat would hurt him more than anyone else. It could prove a hammer blow to any leadership ambitions he may harbour.

Read more: http://www.businessspectator.com.au/article/2013/5/20/policy-politics/combet-vs-shorten-battle-brewing#ixzz2TpERlK9n