Both Act and United Future seem destined for the knacker's yard. The Maori Party's chances seem almost as slim. The Conservative Party is virtually an unknown quantity. Where is John Key to find the parliamentary votes to give him a working majority?
New Zealand First, if they cleared the 5 per cent threshold, might or might not be prepared to do a deal but Winston Peters might be equally tempted by the prospect of joining a new government and making a fresh start as Foreign Minister. His decision in that regard would be made much easier if a Labour-led coalition could show that, even without New Zealand First's support, it commanded a greater share of the popular vote than the National grouping.
This takes place against a background where the Government's greatest advantage - the Prime Minister's personal popularity - is a wasting asset. There are only so many times one can go to that well before it runs dry. "Trust me" works well until the day that trust is exhausted - as former Labour Prime Minister Tony Blair discovered when the truth was finally known about the Iraq war.
All of these considerations and uncertainties present themselves for National without any further deterioration in the polls and at a time when the only alternative as Prime Minister was unable, by his own admission, to show he was a credible option. Imagine how a new contender, able to demonstrate the necessary credibility, could transform what is a difficult situation for National into one that is very favourable to Labour. Another few percentage points are all that is needed.
It is a measure of David Shearer as a man that he will have done precisely this calculation. He will have concluded that a new leader - and a leader recognised as a potential Prime Minister - would provide all that is needed for a Labour election victory, and he has accordingly acted in the interests of the party and, as he sees it, of the country as well.
His personal sacrifice places a special responsibility on those who will play a part in the Labour leadership election to make that sacrifice worthwhile. The party will congratulate itself on having changed the election process so as to give itself the best chance of electing a leader who can take them to victory.
The great advantage of widening the franchise, so as to give party members and affiliates as well as MPs a vote, is it creates an electorate that is able to stand back from personal and partisan concerns and to put the interests of the party first.
I have participated (in the British Labour Party) in several leadership elections - on one occasion as a contender. I have had experience of elections conducted both with the franchise restricted to MPs and also when the franchise has been widened.
The benefit of the wider franchise is that personalities matter less and (hopefully) ability matters more. Within the hothouse atmosphere of the caucus, every vote matters greatly and the temptation is to allow all sorts of personal considerations - ancient grudges, favours to be repaid, long-standing friendships - to sway voting intentions.
With a wider electorate, especially one that includes thousands of party members, individual votes matter less and a broad consensus about what is important to the party matters more. That is now the opportunity that presents itself.
The good news for Labour is the likely contenders all seem to have what it takes. The leadership contest is a welcome exercise in democratic participation and it is an essential step in offering New Zealand voters a real choice as to who should form the next government.
Bryan Gould is a former British Labour MP, and former vice-chancellor of Waikato University.
