The red-blue duopoly has depended on voters being psychological hostages of the idea that the choice at general elections is a binary one. They lose that grip on the minds of the electorate when challenger parties have a credible chance of securing representation. Rob Ford, professor of politics at Manchester University, has coined a neat name for this phenomenon. He calls it the “Tinkerbell effect”. If people stop believing the old parties are invincible, they become beatable. If people start believing that challenger parties can win, that belief becomes self-fulfilling.