Big surprises in Thursday’s British election. For weeks the pre-election polls showed a statistical tie in popular votes between Prime Minister David Cameron’s Conservative Party and the Labour opposition led by Ed Miliband. It was universally agreed that neither party could reach a 326-vote majority in the House of Commons. A prominent British political website projected that Conservatives would get 280 seats and Labour 274.

But the exit poll, released when voting ended at 10 p.m., projected Conservatives with 316 seats and Labour with only 239. It showed the Scottish Nationalist Party sweeping 58 of Scotland’s 59 seats and the Liberal Democrats, the Conservatives’ coalition partners for five years, reduced from the 57 seats they won in 2010 to 10 this time. That turned out to be pretty close to the mark. The main error was that even this underestimated the Conservative wave.