The recent rule changes may instead result in the election of someone - Cunliffe to be precise - who caucus members may regard as being inflicted upon them as leader by misguided outsiders. The caucus - or at least the majority of its members - may thus not feel obliged to take "ownership" of the new leader.
The consequences of that - a flood of MPs announcing their retirements might be one outcome - can only be guessed. But they are unlikely to be positive.
Similar reservations apply to the new rules which prescribe how MPs deal with a leader who no longer enjoys their confidence.
It has gone completely unnoticed that the clause in the new rules approved amid much acrimony at last year's party conference and dealing with the removal of a leader was short-circuited by the caucus in David Shearer's case.
And with very good reason. Shearer was strongly urged by colleagues to resign rather than - as stated in the new rules - face a caucus motion which if passed by the requisite numbers - 50 per cent of the party's MPs plus one - would have triggered a leadership election once the party's president, Moira Coatsworth, had been notified.
That Shearer went quickly and quietly was a blessing not only for him, but for the caucus and the party.
The alternatives do not bear thinking about. What if it had proved difficult to get sufficient numbers to pass the required motion?
Worse, imagine the paralysis which would have struck the party had Shearer done a Helen Clark and dug his toes in and reserved his right to fight the election triggered by that motion.
Had Shearer not played ball, Labour might have found itself embroiled in an ugly and divisive four-way tussle over the leadership which, because of the complicated new method of electing the leader, would have lasted a minimum of three weeks.
Imagine what would happen if Cunliffe becomes leader and that leadership turns into a disaster, but Cunliffe refuses to go and there has to be a caucus motion to force an election.
Shearer would have lost that election. However, in Cunliffe's case, the party might revolt against the caucus and reinstall him as leader to the caucus' horror. Unlikely, but not impossible.
Regardless, the new rules have been symptomatic of an increasingly toxic relationship between the bulk of the caucus and factions within the wider party.
Things have not been helped by Shearer's scuttling of the so-called "man ban" which would have opened the door to women-only candidate selections in some seats - and which Cunliffe has not ruled out reinstating.
Those tensions boiled over at last year's conference - and are likely to do so again if Cunliffe misses out on the leadership, especially if he has the backing of a significant majority of the 40 per cent segment of the overall vote determining the leader which has been allocated to the several thousand paid-up party members.
Unfortunately for party unity, Cunliffe's legendary unpopularity in the Labour caucus is thought to have given Robertson, Labour's deputy leader and Wellington Central MP, the support of around 22 of the party's 34 MPs.
That would give Robertson a substantial chunk of the 40 per cent of the leadership-determining total vote allocated to the caucus - and correspondingly reduce the share of the membership vote Robertson will need to win to become leader.
The other 20 per cent of the "electoral college" vote is held by trade unions affiliated to the party.
Fearful that National will seek to portray the new leader as a puppet of the unions, Labour's supreme body - the national council - has banned block voting by the affiliates and stipulated that their ballots be conducted at delegate or member level.
It would be surprising if Robertson did not pick up a fair measure of support from this quarter, thereby upping the pressure on Cunliffe to win even more of the share reserved for rank-and-file members.
A large number of party activists are backing Cunliffe partly because they see him as the only candidate who can galvanise wavering voters into ending their infatuation with John Key and returning en masse to Labour's fold.
Cunliffe is also being touted as some kind of heir-apparent to the iconic figures of Labour's past and thus someone capable of resurrecting and revitalising Labour's long-dormant left-wing tradition.
This personal transformation has been greeted with both astonishment and scepticism in what might be termed the "Wellington Beltway" element of the party - or perhaps more aptly "Robertson Country" - who assumed Cunliffe was far more at home on the party's right.
Having instead cleverly positioned himself on the party's left which is under-represented by senior MPs, Cunliffe and his supporters are seeking to make his campaign an unstoppable force which makes it impossible for him to be denied the leadership for a second time and which will thus force MPs and union affiliates to shift their support away from Robertson.
As yet no MP with real influence has endorsed Cunliffe. If that starts happening, it will be a sign that pressure is starting to tell.
The leadership battle is starting to tell in other ways - most noticeably in Parliament. With the outgoing leader absent on leave, his deputy consumed with his own bid for the top job and the rest of the caucus viewing developments on the leadership front with increasing trepidation, Labour is drifting leaderless and rudderless for the next two weeks until the new leader is unveiled. The party has become the Mary Celeste of Parliament. Nobody's home.
