To liken Labour's capacity for damaging itself to that of lemmings might seem unkind to lemmings.

But with an awful lot of water to still go under the bridge before the 2014 election, it seems it is never too early for the party to go looking for bridges to jump off.

Its predilection for such self-destructive behaviour was on vivid display at its conference during lengthy sessions devoted to okaying a drastic revamp of the party's outdated structure and constitution.

The "modernising" was all about "empowering" rank-and-file members by giving them a say in choosing future party leaders and imposing tighter obligations on MPs to implement party policy.

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The revamp was achieved. And the party will be the better for it - at least in the longer term.

But at what cost in the short term? What was astonishing was that in the rush to "democratise" the party, the conference backed rule changes which have made it a lot easier for David Cunliffe to mount a coup against the incumbent David Shearer. Or did so until the latter delivered a pearl of a speech yesterday and decided to call Cunliffe's bluff.

While the nobbling of Shearer was deliberate on the part of many delegates, many more were in raptures over the leader's speech seemingly oblivious to the fact that they had plunged a knife into his back the day before.

Shearer's failure to anticipate that the rule changes could leave him isolated and vulnerable is being blamed on party president Moira Coatsworth and general secretary Tim Barnett.

They might take some of the blame for Saturday's chaotic debate on the constitution - which rapidly turned into open warfare between the leadership factions. But the debate was always going to be messy.

What it proved was Shearer does not have control of the wider party. Yesterday's speech has reinforced his control of the caucus, however.

With Shearer now set to confront Cunliffe head-on in the next few days and settle the leadership question once and for all this side of the 2014 election, control of the caucus is what matters for now. The quality of Shearer's speech must have been a shock for Cunliffe, who had been preening himself in front of any passing camera, a veritable peacock in full feather were it not for the nakedness of his ambition.

Presuming Shearer wins a leadership vote in coming days or Cunliffe fails to mount a challenge, the latter will be disciplined by removal from Labour's front-bench.

The weekend's mayhem has given Shearer a much-needed opportunity to show there is iron running through his veins.

But the downside is potentially far bigger than any upside. Labour has not argued in such public fashion since the party's internal schism over Rogernomics in the late 1980s. And the only winner from that acrimony was the National Party.