As its Westminster rally opened, the anti-EU Grassroots Out campaign briefed excitedly about a “special guest”. Speculation flowed about the identity of this talisman: a cabinet minister, a trade union leader, a backbench grandee? No, to the incredulity of those present, it was George Galloway.

Introduced by Nigel Farage as a “towering figure”, the former Respect MP’s arrival triggered an immediate walkout among the audience. They, like others, couldn’t quite believe that the man who fawned over Saddam and Assad, who defended Julian Assange against rape allegations (suggesting he was merely guilty of “bad sexual etiquette”) and who once said of Farage, “[His] Aids smear should disqualify him from any civilised company henceforth” (a category from which Galloway perhaps exempts himself), had been anointed as their saviour.

Other than their opposition to the EU, those backing Brexit are most obviously united by their unpopularity. Galloway, Farage, Michael Gove, Iain Duncan Smith - these are 15 per cent, not 50 per cent politicians. Their approval ratings are poor when not subterranean. By contrast, the In campaign can deploy David Cameron (a still-popular prime minister who speaks with the weight of his office), Theresa May (likewise), Alan Johnson (“best PM we never had”) and Chuka Umunna (who polls particularly well among focus groups) - even if Nick Clegg, Jeremy Corbyn and Peter Mandelson help redress the balance.

The importance of individual politicians is overstated by the media. This is a referendum, to echo Tony Benn, that will be determined by the issues (the economy, security, immigration), not the personalities. But in a close contest (as polls suggest this will be), the margins matter.

There is just one figure left who could notably improve the Out campaign’s standing: Boris Johnson. Polls have consistently shown the Mayor of London to be the country’s most popular politician (a status that reflects his lack of responsibility, some Tory MPs grumble). An Ipsos MORI survey this week found that only Cameron would have a bigger influence over how the public voted. There is no politician that the In campaign fears more. He can reach parts of the electorate that other Tories can't, boasting the invaluable talent of making voters feel good about themselves.

Having teased the media for months about his intentions, it is now decision time for the Mayor. He is, according to some Tory MPs, privately supportive of EU membership but his overweening desire to become Conservative leader could lead him to back Brexit (so inimical to Brussels are the party’s grassroots that Liam Fox recently topped a members' poll). And when a campaign lauds Galloway as “special” (which he is in one sense), there is little doubt that the time has come to send for Boris.