How union support could be crucial to Scottish Labour leadership candidates

In every race, prospective candidates need the backing of a specific number of unions to stand.

They tend to make these up quite easily and focus more on getting the support of parliamentarians.

But in the upcoming Scottish Labour leadership contest, trade union support is in demand.

To make it onto the ballot paper, candidates need the backing of three MPs, three MSPs and three affiliate organisations, two of which must be trade unions.

There are currently three - and potentially four - people standing for the Scottish Labour leadership.

There are 10 trade unions affiliated to the Scottish Labour Party.

In theory, that’s enough for five candidates to have enough endorsements to stand.

In practice, it is not so simple. Like politicians, unions tend to have their own political alignments, and personal relationships also come into play.

A crowded field could mean that a candidate who is popular with parliamentarians fails to make the ballot because of little trade union support.

For example, Michael Marra’s backers are “confident he’ll get support of multiple unions”.

These would be expected to be the GMB Scotland, Community and the Union of Shop, Distributive and Allied Workers (Usdaw).

Mr Marra is a member of both GMB Scotland and Community, while his campaign co-chair Tracy Gilbert was previously Usdaw’s Scottish Regional Secretary.

But the issue for Mr Marra is that Joe Fagan is competing for the same unions.

In fact, Mr Fagan’s supporters are confident he secure the GMB Scotland nomination. Like Mr Marra, he is also a member.

Read more: Key Anas Sarwar ally backs Joe Fagan for Scottish Labour leader

With just three more moderate unions between two candidates, it could mean that Mr Marra or Mr Fagan does not have enough union backers to make the vote.

Getting union support should be easier for Monica Lennon - or Katy Clark if she decides to stand.

Unison, Unite, the Communication Workers Union, the Associated Society of Locomotive Engineers and Firemen (ASLEF) and the Transport Salaried Staffs' Association (TSSA) are generally considered to be more left-wing unions.

This means they are much more likely to back Ms Lennon or Ms Clark, who are the candidates on the left of the party.

Ms Lennon is a member of the GMB, Unite and the CWU. Ms Clark has no union membership on her Scottish Parliament Register of Interests.

Read more: Monica Lennon confirmed as MSP and 'has numbers for leadership race'

If Ms Clark does not stand, it would give Ms Lennon a free hit and she would be almost guaranteed to hit the threshold.

Scottish Labour has two more affiliated unions which are harder to predict.

The Nation Union of Miners (NUM) and Musicians’ Union are much smaller than the others, and could potentially go to any candidate.

So one of these could bail Mr Marra or Mr Fagan out if they don’t get two nominations from the other unions.

Unions will begin to announce their nominations next week.

If one of the candidates fails to hit the required number, but has more backing from parliamentarians than others, there will likely be outrage and calls for a change to the system.