How did pollsters get Trump’s victory so wrong?

Was Donald Trump’s win unexpected? Not if you followed the betting markets, which had Trump at a two-thirds chance of winning days out from the election. The polls, on the other hand, told a different story. Analysis of polls carried out in 15 competitive states in the three weeks before last Tuesday’s election shows that whatever the method of polling used, there was a clear and consistent bias in favour of the Democrats.

Pollsters spent an estimated half a billion dollars (£388 million) on this election, but most polling methods were still biased towards Kamala Harris by around three percentage points. One method – recruiting participants by mail – managed to be wrong by a whopping 13 points. Another, recruiting participants while they were online or using an app, was only off by around one point.