Sir Menzies Campbell’s successor as Liberal Democrat leader looks set to emerge from a head-to-head battle between Chris Huhne, who has already run a leadership campaign, and Nick Clegg, a popular figure among MPs who has yet to put down deep roots with activists.

Although bookmakers made Mr Clegg the odds-on favourite, party insiders expect the race to be extremely tight. Factors such as the length of the campaign and the single transferable voting system could be as important in deciding the winner as the candidates’ charisma and policy platforms.