It is a happy consequence of the Coalition Government’s legislation creating fixed five-year parliaments that this exhibition can be timed precisely to coincide with a general election campaign. In the years when it was in the prime minister’s gift to give a minimum notice of 17 working days of a poll, such topicality would have been achieved by coincidence.This highly enterprising show (to 28 June) draws on the Manchester gallery’s extensive collections (it holds several major national archives, among them that of the Labour Party). It begins by detailing the role of monarch, government, opposition and electorate and the rules which govern them – from the monarch’s constitutional status to the amounts of money that, by law, parties and candidates may spend i