Labour leader David Shearer goes into his caucus showdown today needing to make a clean kill.
The trouble is, he can't.
The tyro Labour leader, who has been in the job less than a year and in Parliament only slightly more than three years, needs to lance the festering boil of discontent around New Lynn MP David Cunliffe and Mr Cunliffe's apparently dwindling band of supporters.
The alternative to a clean kill is months of destabilisation in which both men and their respective supporters reduce each other to the political equivalent of roadkill.
If this happens, watch for deputy leader Grant Robertson to step carefully over the corpses and take over the leadership by autumn 2013.
Mr Shearer’s problem is he cannot make a clean kill without alienating the wider party. The constitutional changes made at the party conference over the weekend give members and the unions more power over caucus.
They are an expression of Labour rank-and-file dissatisfaction with their caucus: with the group of MPs who have been in Parliament too long and also – note this for future developments – because they want a more left-wing government than Helen Clark’s 1999-2008 administration.
Mr Cunliffe has been a vehicle for that dissatisfaction from the Labour Party at large. But commentators who wrote up the constitutional changes as an expression of the wider party’s desire for his leadership got it the wrong way round.
Rather, the push behind Mr Cunliffe is an expression of many Labour members' – who are far more left-wing than their MPs – desire for a more radical government.
One of the many ironies of this is they are using him even more than he is using them.
But too strong a strike at Mr Cunliffe and his supporters – Waikato-based MPs Nanaia Mahuta and Sue Moroney have been specifically named – will be seen as a two-fingered salute by Mr Shearer to the party at large.
That would put the noose around his own neck come February, when those constitutional changes take effect.
But too weak a strike and he looks like a wuss.
So it will be summer of simmering unrest and plotting around the barbecues. There will be more public explosions from MPs on both sides of the grouping.
And by late summer, look for Mr Robertson to sigh wearily and to come forward – for the good of the party, of course – and shoulder the burden of cleaning up the mess.
Mr Robertson is a former Helen Clark staffer and is from the party's gay/bi friendly Rainbow faction. Were it up to caucus he would probably be complemented by electing someone to the deputy role who at least looks the part of a "red-blooded male".
Waimakariri MP Clayton Cosgrove would fit the bill well – and he is a more effective opposition MP than at least four-fifths of the Labour caucus – but is not widely popular.
In any case, whether that will happen as the party organisation takes greater control from February next year is a very open question.
With a determined push from Labour members at the conference in more left-wing directions – remits to curtail private education and to give local councils greater powers were passed, for example, and there is a strong push for a much more interventionist economic policy – the party at large is likely to see any such move as pandering to rednecks.
In short, whatever the outcome of today's stoush, the political scene has only witnessed the start of Labour's latest war of the succession.