THE local elections on May 4th were good for Theresa May and bad for everyone else. The Conservatives recorded the best performance of any party in national government for over 40 years, gaining a net 563 seats and winning control of 11 councils, as well as new mayoralties in the West Midlands and Tees Valley. Labour did badly, with net losses of 382 seats and seven councils, although at least the party convincingly won the mayors’ races in Liverpool and Manchester. The Liberal Democrats lost a net 42 seats. And the UK Independence Party (UKIP) was almost wiped out, losing 145 seats and ending up with but one lonely new councillor.

Based on these results John Curtice of Strathclyde University projects national vote shares of 38% for the Tories, 27% for Labour, 18% for the Lib Dems and 5% for UKIP. These shares are much closer than the latest opinion polls, which give the Conservatives a whopping lead of as much as 20 points. Looking at the local results and the poll numbers, some pundits reckon Mrs May is heading for a landslide victory on June 8th, with a majority in Parliament of 140 seats or more.

Yet some pollsters are more cautious. Anthony Wells of YouGov warns against reading across from local to general elections. When both are held on the same day, as in 2015 and 2010, fully a quarter of voters split tickets between parties. In 1983 and 1987, the two previous occasions when a June general election followed local contests in May, the results were very different (though in both these cases the Tories actually did better nationally). Bitter experience shows that opinion polls have often proved unreliable.