Cunliffe also needs to stem whispers Labour has already given up on 2014. David Shearer and Phil Goff both felt short-changed on the honeymoon front, and so far Cunliffe has been equally unsuccessful at getting the Bridezilla Voters up the aisle. The polls haven't budged.
To McCarten will fall the role of trying to build caucus unity, a job best achieved by deploying bribery and fear.
There have been rumours the ABC (Anyone But Cunliffe) Labour MPs want to ensure Cunliffe gets a pasting in the election so they can roll him afterwards. The strategy these people are said to have adopted is to be lazy. The counter-theory is that this plot by the ABCs has been fabricated by Camp Cunliffe supporters to set up the ABCs in advance as scapegoats in case of a dire election result.
It is easy to spot a motive for the ABCs: utu. When Cunliffe said on Radio NZ that his caucus was united behind him he gratuitously added that the same could not be said of the reigns of his recent predecessors. Eyebrows were raised, along with the old saying that when you point a finger at someone, three of your fingers are pointing back at you.
It was, after all, Cunliffe and his merry men and women who were blamed for not putting their heft behind Goff and Shearer. Some of that was unfair, but some of it was also fair.
Motive or not, the evidence the ABCs are on self-imposed glide time is rather thin. The ones whose footsteps have worn Press Gallery carpets threadbare touting hits on the Government or policies are the likes of Shane Jones, Phil Goff, Chris Hipkins and David Shearer.
Goff has always been a hard worker and hasn't changed. Jones has finally answered to the "lazy" tag that has dogged him throughout his political career with an energetic assault on the supermarket industry.
Hipkins has been agile on charter schools and organised a visit for Cunliffe to promote early childhood education policies. It was an ABC (or at least, a Grant Robertson supporter) - Jacinda Ardern - who came up with the child payments policy Cunliffe made the centrepiece of his state of the nation address. The subsequent error in judgment of not openly disclosing the paid parental leave disqualifier can hardly be slated to Ardern.
Meanwhile, barely a "hi-de-hi" has been heard from most of the Camp Cunliffers such as Nanaia Mahuta, Moana Mackey and Iain Lees-Galloway. Cunliffe himself has been less high profile than some of the ABCs.
It is also becoming clear Cunliffe's left tack should concern the Greens. The Green Party's drop in the TVNZ Colmar Brunton poll could be a rogue result, or a short-term reaction to co-leader Russel Norman's playtime at Dotcom's.
But it could also be a sign left voters are migrating back to Labour at the glimpse of a summer. In theory the broad centre-left vote is most important to Labour, regardless of how it is spread. But Labour will be trying to ensure as much as possible is spread on their slice of bread, relegating the Greens to crusts.
Labour knows there is public unease about having a weak main party heading a coalition. That could impact on the centre-left vote. Cunliffe was asked about the power of the Greens relative to Labour on Radio NZ and said three times Labour expected to be at "the heart" of a future government, an effective admission other parties would be vital organs rather than simply useful appendages.
It sparked an image of Cunliffe putting together a Mr Potato Head coalition, trying to ram the other parties into their appropriate places to make a working body. He has lined up the Greens to be the sensitive nerve system and NZ First for the spleen. Hone Harawira's excess of hot air makes him the front runner to be the lungs.
As for McCarten, Cunliffe clearly hopes he will supply the brain and backbone.
