In a couple of places the Tory leader stumbled, almost as if his argument didn’t interest him. Yet he at least sounded more convinced than his two main rivals, Nick Clegg, leader of the Liberal Democrats, and Ed Miliband, leader of the Labour Party, both of whom have also uttered stiff words on immigration this month. Mr Clegg, who is Mr Cameron’s coalition partner, renounced a long-standing Lib Dem proposal to grant an amnesty to longtime illegals. Mr Miliband reiterated his regret that the previous Labour governments, under Tony Blair and Gordon Brown, had taken such a laissez-faire view of the matter—allowing net immigration to rise by 2m in a decade. Still two years from the next general election, a grim pattern has emerged. Immigration, once unmentionable in polite political circles, will be one of the big issues in a painfully protracted campaign.