"If Hitler invaded hell I would make at least a favourable reference to the devil in the House of Commons,” Winston Churchill remarked shortly after the Nazis’ fateful decision to open a second front against Soviet Russia.

It’s tempting to see that as the justification behind George Galloway appearing as the “very special guest” at Grassroots Out’s rally on Friday.

The appearance of the Respect leader and former MP attracted derision from the commentariat and prompted walk-outs from the hall. But signing up Galloway is an astute move on the part of Grassroots Out that could have big implications for the coming referendum.

Why? Grassroots Out is currently in a fight to the death with Vote Leave, another pro-Brexit grouping, for the status of “lead campaign”. The designation brings with it a spending limit of £7m during the referendum’s “regulated period” – all other registered campaigns will be able to spend just £70,000. Effectively, whichever campaign doesn’t get the designation will have to shut down.

Although Stronger In has no official line on which of the two campaigns it would rather face, it is an open secret that they regard Vote Leave as the deadlier opponent.

Matthew Elliot, formerly of the Taxpayers’ Alliance and the successful campaign against the Alternative Vote, has been the victim of a whispering campaign from his own side but is feared and respected in equal measure by his opponents. Many either have pleasant memories of campaigning against the Alternative Vote alongside him or bad ones of the two-to-one defeat that was handed to the Yes side. Dominic Cummings, formerly of Michael Gove’s office and the successful architect of the defeat of the North-East Assembly, is held in similar esteem.

“If it’s [Grassroots Out], then it will be a very narrow campaign with a ceiling of 40 per cent of the vote,” one senior staffer predicts, “If it’s Elliott it will be a vicious campaign of smear and fear – and I’d put our chances at 50/50.”

But Vote Leave’s chances of making it to the campaign proper are themselves no better than “50/50” according to one source with close knowledge of the Electoral Commission’s process. Unlike the Boundary Commission, which has a standing brief to seek to create marginals when reshaping seats, the Electoral Commission has no mandate to pick a candidate based on its percieved strength at Westminster or the feelings it inspires among its opponents.

Instead, the deciding factors are “breadth of support” among supporters of whichever outcome – Remain or Leave – that campaigners are seeking.

Vote Leave has secured heavyweight Conservative support – the six Cabinet ministers who will back Brexit, Michael Gove, Iain Duncan Smith, Chris Grayling, John Whittingdale, Theresa Villiers and Priti Patel all appeared for a photo opportunity at Vote Leave. It still retains the loyalty of John Mills, the Labour donor, and Graeme Stringer, a Labour MP, and will add to that the support of Frank Field, another Labour MP. It has a smattering of Ukip heavyweights, including Suzanne Evans and Douglas Carswell, the party’s only MP. In a futher coup for Vote Leave, Jenny Jones, the Green party’s only representative in the House of Lords, is also a member.

That should be enough to put Grassroots Out and Leave.EU, the two groups that will seek designated campaign status as a “supergroup”, out of contention as a serious contender.But Grassroots Out have secured the support of the bulk of Labour MPs who back a Leave vote, a number of Conservative MPs, and Ukip’s leader Nigel Farage. They have also focused extensively on growing their social media presence. Leave.EU has 474,140 likes on Facebook. Vote Leave has just 169,349. On Twitter, Vote Leave has in excess of 19,000 followers. Leave.EU has just under 63,000.

Grassroots Out will claim that they represent “true” Leave feeling in the country at large against a campaign that they will claim exists mostly in the Westminster bubble. Against that, Vote Leave has already appointed staff out in the country to work on voter mobilisation.

In addition, Grassroots Out has been bolstered by the strength of feeling against Cummings, a key player in Vote Leave. Although, as with Elliott, Cummings is respected by his opponent, he is the subject of resentment among many who have abandoned Vote Leave in favour of Grassroots Out. There is a belief that this may fatally hamper Vote Leave’s hopes of meeting the following criterion for designated campaign status, set out by the Electoral Commission:

“how you plan to represent other campaigners for the same outcome including how you would engage with them”

And Galloway, for all his not inconsiderable baggage, represents an underappreciated asset for Grassroots Out’s chances, something that the Electoral Commission appreciates better than many others.

The relevant section in the campaign criteria is this (emphasis mine):

“How you intend to convey your campaign message across to voters across the UK and Gibraltar including how you will make use of the lead campaign group benefits. You may wish to consider how you will communicate with different groups of voters such as different age groups (including younger voters), voters with disabilities, ethnic communities and those not using English as their first language”

Galloway has a presence on RT, Press TV and a variety of ethnic minority television channels that, while neglected by the mainstream, gives a campaign with his support a far stronger response to that criterion than its opponents. “Breadth” of support remains Grassroots Out’s ace in the hole.

That said, for all Grassroots Out has a stronger chance than many thought possible - a year ago, I wrote that it was inevitable that Vote Leave, then Business for Britain, would be the movers and shakers behind an Out vote - the Electoral Commission will be reluctant to risk nobbling what is widely seen as the more effective campaign. As one insider puts it, “a thousand angry emails” from Leave supporters in the country is a less daunting prospect than turning down the claims of the influential Vote Leave, though the case for both on paper is “finely balanced”.

Should Grassroots Out prevail, their much-maligned special guest will have played a bigger role than many understand.