Their task has been slightly complicated by Labour’s new rules. Union members are no longer automatically eligible to vote for the party leader, but can sign up as “affiliates” whose votes carry as much weight as full party members. Hence Mr McCluskey desperately trying to sign up Unite members in the hope of stacking the decks in Mr Burnham’s favour. Hence, too, Harriet Harman’s announcement that the wider public can affiliate and vote on the leadership for a fee of £3. The cynical intention may well be to dilute union power in the election, but anything that encourages more people to involve themselves in politics is to be welcomed.