For three years, Phil Goff has tirelessly pushed his boulder Sisyphus-like up the hill, only for it to roll back down each time. Now, however, the rock may have slid down the hill one too many times.
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 clearly think November's election is a foregone conclusion, and are now focusing on what happens afterwards leadership-wise, positioning themselves accordingly.
The net effect of this is to leave Phil Goff marooned exactly where National wants him - in 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 Goff offered to resign as leader during a recent meeting of Labour's front-bench MPs.
What Goff apparently said was that he had put everything into the job for the past 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 Goff before 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 that even among those intending to vote Labour, many do not believe Goff can win the election.
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 upcoming televised leaders' debates.
The hope is that Goff will shine in similar unexpected fashion as did two former Labour leaders - Bill Rowling in 1978 and Helen Clark in 1996. But both still lost.
Goff starts from a long way behind. His ratings as preferred prime minister have remained near rock-bottom 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 Clark in late 2008.
On the crucial questions of whether he is a capable leader, good in a crisis and having sound judgment, Goff's initially positive ratings have slumped.
The resurrection of Clark and Rowling had a lot to do with their National opponents. Jim Bolger was never held in high regard by voters, and Rowling's reasonableness proved a welcome antidote to Rob Muldoon's abrasive style.
Goff, however, is up against someone whose positive ratings have gone through the roof and helped keep National's support at a consistently high level since the last election.
The question is whether Key can do what Clark had a chance of doing in 2002 and secure an absolute majority.
Clark's failure is being cited as precedent for Key likewise stumbling - the suggestion is that voters will no longer give one party sole rights to the exercise of power.
But the circumstances are very different. While 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. It refuses to deal with Winston Peters, but neither his party nor United Future is needed.
The moderating force stopping National from getting too radical and drifting towards Act's solutions resides within National itself.
Key's classic conservatism is in sync with middle-ground voters who, as a group, have always leaned slightly to the centre-right - something Clark understood.
Allowing for wasted votes for minor parties which do not cross the threshold, National probably needs around 48 per cent of the party vote to be able to govern alone. It secured 45 per cent in 2008.
While much is made of the 1951 election as the last time a party won more than 50 per cent of the vote, National has topped 47 per cent in seven of the 22 post-war elections.
It is also worth noting that Labour, in winning a second term in office in 1987, raised its vote from 43 to 48 per cent.
In those elections minor parties were heavily disadvantaged by the pre-MMP electoral system. But today's minor parties are struggling even with MMP.
National, however, does not want to look too cocky, and is playing down its chances of gaining an absolute majority.
And even if it does, Key is saying he will still try to stitch together power-sharing deals with minor party allies.
This would not be an act of generosity. It would be insurance that it will be able to still count on those parties' backing in 2014 - an election which will be a lot harder for National to win than the upcoming one.
When the positioning going on within Labour is taken into account, what is happening is that the early stages of the 2014 election campaign are being played out before this year's one has started.
All rather bizarre, to say the least.