The Labour electoral college for the leadership has three components to it. Two of them are simple and one is complex. Also a complicating factor is that with three candidates, it is a preferential ballot.

Let’s take the three sections one by one.

Caucus Vote

The caucus gets 40% of the vote. They used to get 100%. They are the ones who actually get led by the Leader, and have to work with the leader on a day by day basis.

There are 34 MPs, so effectively each MPs vote is worth 1.18% of the total vote. If the vote is after Lianne Dalziel resigns then there are 33 votes worth 1.21% each.

Members Vote

They get 40% of the vote. Labour have not revealed how many members they have, but let’s say it is 10,000. If they all vote they get 0.004% each. So an individual vote counts for little, but the overall vote of the members does count for the same as the caucus.

Union vote

The affiliated gets 20% of the vote. This is proportional to the number of affiliated members each union has. Again this is not publicly known but we can estimate it. Basically the number of affiliated members is their total number of members multiplied by what percentage voted to affiliate with Labour when they voted to do so. This by definition is a proportion between 50% and 100%.

If we assume all the unions had a similar proportion in favour, then we can estimate their relative voting strength based on their latest returns of members to the Registrar of Unions. The six unions in order of size are:

1. EPMU (Engineering etc) 36,987 members, 41.5% of union vote, 8.3% of total vote
2. SWFU (Service Food etc) 22,351 members, 25.1% of union vote, 5.0% of total vote
3. MWU (Meat) 15,313 members, 17.2% of union vote, 3.4% of total vote
4. DWU (Dairy) 7,000 members, 7.9% of union vote, 1.6% of total vote
5. RMTU (Rail) 4,747 members 5.3% of union vote, 1.1% of total vote
6. MUNZ (Maritime) 2,635 members, 3.0% of union vote, 0.6% of total vote

As one can see the power of unions such as the EPMU and SWFU is considerable and they could well decide who the winner is. This is what happened in the UK Labour Party 2010 election. Ed Miliband won only 46% of the members vote and 47% of the caucus vote but got 60% of the union vote and beat his brother David Miliband. So the elected leader had minority support from both members and caucus, but got there thanks to the unions. The unions actually broke Labour’s rules by including promotion material for their preferred candidate in the same envelope as the voting paper!

But the situation is even worse in NZ Labour, than UK Labour. In UK Labour the unions allow all their members to have a vote. Ballot papers went out to around 2.7 million union members. This diluted the power of the union hierarchy to affect the ballot. They certainly endorsed candidates, and their endorsement won the day for Ed Miliband, but it was still a 60:40 split.

NZ Labour has decided that it is up to each union as to whether all their members will vote, or just their national conference delegates. Only one union, the SWFU, is allowing all members to vote. Good on them for doing so.

The other five unions are having their conference delegates vote only. So how many people is this? Well I’ve gone through the rules for each union to try and estimate this.

1. EPMU – 1 delegate per 1000 members, 45 delegates
2. SWFU – full membership vote
3. MWU  – 1 delegate per 350 members, 54 delegates
4. DWU – 1 delegate per site with more than 30 members, estimate 70 delegates
5. RMTU – determined by previous conference so unknown
6. MUNZ – 1 – 4 delegate per branch (13 branches), estimate 30 delegates

The power of those 45 EMPU delegates is considerable. That is a small enough number for them to meet collectively and decide who to support. Of course it is a secret ballot and they can vote however they like, but as loyal delegates they will vote for what is best for the EPMU. Those 45 EPMU delegates will be worth 8.3% of the total vote. I doubt they will be splitting 50/50 or even 60/40. I predict 80/20 or 90/10 or more.

Each EMPU delegate will get approximately 46 times as much of a say as a normal Labour Party member (if they are a member, they get an additional vote in that section also). A MWU delegate will get 16 times the say of a normal Labour Party member.

The 170 or so delegates from the EPMU, MWU and DWU are worth 13.3% of the total vote.  It is hard to see any leadership candidate winning without them. Those lucky 170 delegates will be getting lots of phone calls as they play a major part in picking the person who could be the next Prime Minister.

UPDATE: Very happy for any union to provide the exact number of voting delegates they have, so I can update the post.