The Labour Party is in the process of choosing a new leader because members believed the party could not "win" the election with David Shearer as leader. The problem is under proportional representation the concept of a single party winning an election is virtually meaningless.

The candidates have since tried to clarify this issue by each saying that he is the one to defeat John Key's National-led Government. However, to defeat John Key, Labour doesn't necessarily need more than 30 per cent of the vote, let alone 40-something per cent.

To achieve a change of government, Labour needs the median voter to vote for a party that is unlikely to support the present Government. Thus, their electoral marketing should target the median voter.

Although politics does involve more than a left-right spectrum, nevertheless, in every MMP election so far we can place the various parties on such a spectrum. From left to right, the present Parliament is: Mana, Green, Labour, NZ First, Maori, United Future, National and Act.


In 1996, NZ First had the median MP. It was Labour in 1999, United Future in 2002, NZ First in 2005, National in 2008 and United Future in 2011.

Given that we elected a 121-member Parliament in 2011, the median MP on this spectrum is MP number 61. That representative is Peter Dunne, United Future's sole MP. This means that we have a centre-right government essentially because Mr Dunne has aligned, this time, with the parties to his right rather than those parties to his left.

It also means the result of the last election was very close, given that, if the Maori Party rather than United Future had occupied the strategic middle position, the Government could have been quite different.

To succeed in removing the present Government next year, it will probably be sufficient if NZ First can attain the median position at present occupied by United Future. Indeed a careful reading of the political environment before the deposing of Mr Shearer would be that New Zealand First did indeed occupy that median position. It still seems the most likely option, though possibly less likely as a result of recent events within Labour.

My sense is that, while the Labour vote may increase with its new leader, the likelihood that National will win the critical median position has increased.

To a large extent, Labour has got itself into this position because its strategists may not have fully understood the polls. And let's face it, the change of leadership was poll-driven.

Polls taken in non-election years mainly reflect the preferences of entrenched voters. The really important information is the percentage of those who are undecided; either undecided about who to vote for, or undecided about whether they will vote.

At present, almost everyone who wishes for a continuation of the present Government will say that they will party-vote National. Indeed even electorate supporters of John Banks and Peter Dunne will almost all vote National.

Thus, in 2013 almost all the undecided vote is an anti-government vote. It's just that many people are undecided between Green and Labour, or between NZ First and Labour. The support for a change of government has most likely been understated by the way the poll results have been presented.

We see this before every election. As the undecided voters make up their minds, the smaller anti-government parties generally benefit. This effect is likely to be even more pronounced next year given that the small parties on the right look particularly bereft of support.

The Labour leader most likely to bring about a change of government is the leader who can raise doubt in the minds of centrist National voters. If such voters can be persuaded to vote for any of Labour, NZ First or Green, then we should get a Labour-led Government.

Which does Labour most want? To widen the gap between itself and the country's third-largest party? Or to form a government while having coalition partners that together are almost as big as itself?

My hunch is that many Labour activists would rather be a part of a larger Labour Party in opposition, than a smaller Labour Party in government. Indeed, that may be why David Shearer is no longer Labour Party leader.