All four candidates seeking to take over from Len McCluskey as the leader of Unite have made it through to the ballot of members, the union has said, setting the stage for a tense race with potentially significant repercussions for the Labour party. As expected, Gerard Coyne, who is seen as most broadly supportive of Keir Starmer, has gained enough branch nominations to reach the ballot. Coyne secured 196, above the 172 threshold to proceed – at least 5% of all workplaces and branches – but the lowest of the four. Coyne has called for the union to focus on its members rather than controlling Labour, and is seeking an independent investigation into the use of members’ money to build a £98m conference centre in Birmingham. Steve Turner, who has been close to McCluskey, won the most nominations, with 525. He is seen as the favourite after securing the support of the United Left faction, and has argued for more pragmatism from the union’s leaders. But Howard Beckett, a close aide of McCluskey, was beaten into second place by Sharon Graham, securing 328 nominations against her 349. Beckett, the union’s former legal adviser, was recently suspended from Labour for saying that Priti Patel should be deported instead of refugees. There has been speculation that Coyne’s presence on the ballot would prompt negotiations among the other three candidates, who are aligned more to the left, about whether any of them should drop out to avoid splitting the vote in the first-past-the-post ballot of Unite’s 1.2 million members, letting Coyne win. While sources in the candidates’ camps said attempts had been made by senior figures to persuade Graham to step down, a close associate said there was “not a cat in hell’s chance” she would make way for her two male rivals from the left, and she planned to be the union’s first female leader. Coyne has also condemned the prospect of what he called “a grubby backroom deal between the three continuity candidates”. Turnouts tend to be low – last time just 12% of the union’s members voted – which can result in surprising results. Backroom deals between candidates often take place to help factions to maintain control. Ballot papers will be sent out, with the replacement for McCluskey, who has led the union since 2010, declared on 16 August. The contest will be watched closely by Starmer and the parliamentary Labour party. Unite has been a strong critic of Starmer’s style and politics, and has maintained close alignment with Jeremy Corbyn and his former supporters. Unite has been Labour’s biggest donor and was criticised for having too much influence over the party under Corbyn. The union maintains influence over the party’s ruling national executive committee. Beckett has said he would consider withholding funds from Labour. The election comes after Unison, the UK’s biggest union, and GMB, another major Labour funder, both chose new general secretaries broadly supportive of Starmer.