The Staggers 12 August 2015 600,000 apply to vote in Labour leadership contest - and Corbyn will gain The huge surge in trade union members registering will aid the left-winger's campaign. Labour leadership candidate Jeremy Corbyn attends a rally at the Mercure Cardiff Holland House Hotel on August 11, 2015 in Cardiff. Photograph: Getty Images. Sign UpGet the New Statesman\'s Morning Call email. Sign-up A remarkable 610,753 people have applied to vote in Labour's leadership contest. After extending the deadline by three hours to 3pm, the party today attracted 17,755 new members, 99,703 new affiliated members (from trade unions and socialist societies) and 51,295 new registered supporters. The huge surge in affiliated members appears to confirm reports by myself and others that the unions were holding back members' details until the last possible moment (to the alleged benefit of their chosen candidate, Jeremy Corbyn). The total electorate is comprised of 299,755 full members, 189,703 affiliated members and 121,295 registered members. It is Corbyn, who is already on course to win the contest, who is likely to benefit. The most recent YouGov poll found that he had the support of 74 per cent of affiliated supporters having won endorsements from two of the three big unions: Unite and Unison. One shadow cabinet minister told me that Corbyn could win 60-65 per cent in the first round of voting (up from 53 per cent in the latest poll). If elected, the left-winger will have a huge mandate, making it harder for hostile MPs to justify his removal. The party has emphasised that the "verification process" is continuing after calls by four MPs for the election to be halted over fears of entryism. To date, 1,200 people have been barred from voting after being identified as members or supporters of other parties, with more than 800 under investigation. › Benedict Cumberbatch’s Hamlet, and why there’s now a class war in our theatres George Eaton is senior online editor of the New Statesman. Subscribe For daily analysis & more political coverage from Westminster and beyond subscribe for just £1 per month!