Should Jeremy Corbyn worry about not getting the GMB endorsement?

One of today's big stories is that the GMB union has endorsed Owen Smith for Labour leader in this year's leadership contest, as against no endorsement by them last year. I can partially understand the decision, as GMB represents Trident workers and Owen is pro-Trident renewal whilst Jeremy is anti-Trident renewal, so there is some protecting of their interests involved, but that ignores the fact that keeping Trident is still currently national Labour Party policy and that at its annual GMB congress earlier this year the union called for "clear and unambiguous" support for Mr Corbyn.

It does seem that the buzz about how good having the GMB's support, as one of the UK's biggest unions, is a bit disingenuous given that of the GMB's massive 641,000 members only 43,419 of them voted in the endorsement ballot (i.e. 6.77% of the GMB membership). Of those 43,419 members the 60% who voted for Owen represent 26,051 members, which as a percentage of the total is just 4.06% of the whole GMB membership, which might just take the gloss off the gingerbread slightly. Ballot figures are as given in the BBC News story here: http://www.bbc.co.uk/news/uk-politics-37026145

Meanwhile, there are multiple reports on social media by GMB members who are asking, "what ballot?" as they claim they have not been asked at all, as some of the examples below show:

@GMB_union As a member I haven't received a ballot paper or been consulted on who the Union will back in Labour Leadership race @Tim_Roache

— rob kelsall (@rob_kelsall) August 10, 2016

@rob_kelsall @Rachael_Swindon @GMB_union @Tim_Roache neither has my Hubby..been a fully paid up member for 47yrs

— Christine Taylor. (@Malchris1954) August 10, 2016

@rob_kelsall @GMB_union @Tim_Roache Same here. First I heard was an email about the results, so it's not as though I wasn't contactable.

— ABAC (@AintBigAintClev) August 10, 2016

@rob_kelsall @GMB_union @Tim_Roache me neither! What the hell is going on here???

— Jack Nimrod (@jacknimrod1) August 10, 2016

@ChrisCr711 @caerdyddhome @bentos_j @NEWTEKWORLDNEWS We were not balloted only selected group GMB leadership fix disgraceful disreputable

— Colin J Smart (@colinsmartone) August 10, 2016

@rob_kelsall @GMB_union @Tim_Roache glad I'm not the only one, first I've heard about this vote was today via social media, not good advert

— Ian Hawthorne (@IanHawthorne8) August 10, 2016

Tim Roache, GMB's General Secretary, took to Twitter to refute the claims and to assert all GMB members were balloted:

No. Over 40,000 VOTED. ALL GMB members were asked. The response rate is down to individuals like any other ballot https://t.co/O2n0gpXpeI

— Tim Roache GMB (@Tim_Roache) August 10, 2016

But members in Scotland were excluded from the ballot (has the GMB written off Labour in Scotland?) as this article on the GMB website shows, whilst NewTekWorldNews claims that ​Scotland didn't want to participate in the nominations process.

Regardless of how the ballot was conducted, one thing that did come out of the various figures being bandied about today was that the GMB has only around 30,000 members paying the political levy as part of their membership, so they will be the ones who can actually vote in the leadership election itself once ballot forms are sent out from 22nd August, but will they and, crucially, for whom?