The irony is rich. Very rich. And it will not be lost on David Shearer.
For the very changes in the Labour Party's rules which Shearer's successor, David Cunliffe, was party to and which he promoted in order to undermine Shearer could end up destroying Cunliffe's leadership.
Under Labour's constitution - which was rewritten two years ago - the leader has to seek re-endorsement by the members of the party's caucus within three months of the election occurring.
This obviously poses no problem for a leader who has just won that election.
For a leader who loses it is a very different story.
If the leader cannot secure the votes of 60 per cent of MPs plus one more MP, then the leadership becomes subject to a party-wide vote which includes all party members and affiliated trade unions along with the party's MPs. Cunliffe would likely win that wider vote. Cunliffe's fate, however, is really in the hands of his caucus colleagues, the majority of whom still cannot abide him.
If he does not get re-endorsed by them, his credibility with the public will be completely shot.
If he then stands as a candidate in the party-wide election, he will be seen to be trying to thwart his parliamentary colleagues as well as trying to save his own political neck.
Cunliffe is already trying to avoid being framed in such a negative fashion by saying he would be using a party-wide vote to seek a "mandate" for the "modernisation" of the party.
Such language will be treated with deep suspicion by those party activists who have been seeking to push Labour leftwards and who backed Cunliffe in large numbers in last September's leadership ballot which followed Shearer's resignation.
One option for might-be challengers to Cunliffe would be to endorse him now and trigger a leadership challenge at some later date under another provision in the party's rules which triggers a party-wide ballot if more than 50 per cent of MPs write to the party's president seeking such a vote. Whatever, the required leader re-endorsement vote will have to be brought forward, otherwise Labour will be seen as failing to address the deep-rooted factors which contributed heavily to the party's woeful showing on Saturday.
In addressing those factors, however, there is a very real danger Labour starts tearing itself apart.
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