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For the past three years, Phil Goff has tirelessly pushed his boulder Sisyphus-like up the hill, only for it to roll back down each time.
The rock may have slid down the hill one too many times, however. Over the past couple of weeks cracks have appeared in Labour's united front, giving National added reason to believe it can secure the electoral equivalent of El Dorado - winning enough seats in an MMP election to govern alone.
Labour's legendary self-discipline seems to be crumbling under the relentless pressure of bad polls.
Witness the unfortunate outburst from Dunedin South backbencher Clare Curran flaying the Greens for having the temerity to encroach on territory which apparently belongs to Labour as of right.
Of more serious note, some senior Labour MPs, who clearly think November's election is a foregone conclusion, are now focusing on what happens afterwards leadership-wise.
They are positioning themselves accordingly. The net effect of this is to leave Phil Goff marooned in the exact position National wants him - an ineffectual limbo with his leadership destabilised but not so much that he must be removed before the election.
Most damaging has been the leaking of suggestions that Mr Goff offered to resign the leadership during a recent meeting of Labour's front-bench MPs.
What Mr Goff apparently said was that he had put everything into the job for the last three years and anyone who wasn't happy with his performance should stick their hand up. No-one did.
The only motive for the leak would be to undermine Mr Goff ahead of the election campaign to ensure he loses.
Blame is being levelled at those backing the post-election leadership aspirations of Labour's ultra- ambitious finance spokesman David Cunliffe.
Worse, the leak was followed by a 3 News Reid Research poll which found even among those intending to vote Labour, many do not believe Mr Goff can win the election.
Mr Goff will soldier on. He will give his all during the election campaign. If that turns out to be not good enough, he will step down without having to be prompted.
In the meantime, it is straw- clutching time. Labour stalwarts reassure themselves that the yawning gap in the polls between their party and National will close once voters focus on the election. They argue that voters will get to see the "real" Goff and warm to him when he goes head- to-head with John Key in the televised leaders' debates.
The hope is that Mr Goff will shine in similar unexpected fashion as two former Labour leaders in turn did - Helen Clark in 1996 and Bill Rowling in 1978. Both still lost, however.
Mr Goff starts from a long way behind. His ratings as preferred prime minister have remained at near rock-bottom levels throughout this term.
Voters' ratings of his attributes as a leader - as measured by the 3 News poll - have become more unfavourable since he took over from Ms Clark in late 2008. On the crucial questions of whether he is a capable leader, good in a crisis and having sound judgement, Mr Goff's initially positive ratings have slumped.
The resurrection of Ms Clark and Mr Rowling had a lot to do with their National opponents. Jim Bolger was never held in high regard by voters, while Mr Rowling's reasonableness proved a welcome antidote to Rob Muldoon's abrasive style.
Mr Goff, however, is up against someone whose positive ratings have gone through the roof and helped keep support for National at a consistently high level since the last election.
The question is whether Mr Key can do what Ms Clark had a chance of doing in 2002 - secure an absolute majority.
Ms Clark's failure is being cited as precedent for Mr Key likewise stumbling - that voters will no longer indulge one party with sole rights to the exercise of power.
The circumstances are very different, however. While Ms Clark was widely regarded as a hugely capable prime minister and Labour at that stage was strong on fiscal rectitude, the conservative voters she had to win over to cross the line were ultimately suspicious of Labour's social agenda.
With National's vote collapsing, those voters decamped to United Future and NZ First, in the hope those parties would be moderating forces on Labour.
Those parties are no longer strong enough to be a moderating force on National, which anyway refuses to deal with Winston Peters. Neither party is needed, however.
The moderating force stopping National from getting too radical and drifting towards Act's solutions resides within National itself. Mr Key's classic conservatism is in sync with middle-ground voters who, as a group, have always leaned slightly to the centre-right - something Ms Clark understood.
Allowing for wasted votes for minor parties which do not cross the threshold, National probably needs around 48% of the party vote to be able to govern alone. It secured 45% in 2008.
- John Armstrong is The New Zealand Herald political correspondent.