This Labour Party election breaks new ground in New Zealand politics. For the first time, the leader of a major party in Parliament will be chosen by an electorate larger than the party's MPs. Paid-up members of the Labour Party and delegates of its affiliated unions will together have more votes than Labour MPs. The consequences are unknown.
Quite possibly, Labour MPs will not get the leader most of them want. The new rules were adopted by the party last year as a response to the caucus' choice of David Shearer over David Cunliffe who was a stronger performer in front of the party. That is not to say Mr Cunliffe is a certainty to carry the votes of members and unions over the coming weeks - he faces an equally effective speaker in Grant Robertson - but it is quite possible that most of the MPs will prefer Mr Robertson and Mr Cunliffe will be elected.
The third candidate, Shane Jones, could be the best public performer of them all but he will struggle to win the hearts of party activists or unions. He is casting his net wider than Labour's modern academic and feminist membership, appealing to the "smoko rooms" of yesteryear.
His differences with the Green Party are well known and of the three candidates he may have the most difficulty observing the party's hopeful prohibition of direct criticism of each other.
If Labour is looking for an open debate that will test the mettle of potential leaders, it will need to be prepared for some dissension.