American pollsters aren’t sure they have fixed the flaws of 2020

AS AMERICA ENTERS a nervous election year, one thing is certain: the opinion polls will be watched closely for clues about the outcome. But how much faith should be placed in them? In the past two presidential cycles they misfired, badly underestimating support for Donald Trump each time. Mr Trump looks likely to be the Republican nominee again. In head-to-head polls he leads Joe Biden by 2.3 points on average. That suggests a toss-up. Polls conducted so far in advance of the election have generally missed by a margin far greater than Mr Trump’s current lead.

And Mr Trump’s voters vex pollsters: they appear to be disproportionately less likely to take part in pre-election surveys yet turn out to vote for him. Pollsters have been grappling with ways to reflect this in their numbers, but no one knows how well their adjustments will work. In a close contest, even small errors can prove critical.