Ben Walker in New Statesman:
We “data people” have all been burnt by polling – and it hurts. In Britain, America and elsewhere, there have been enough high profile “misses” by the industry to give anyone cold feet about relying on polls as the sole metric for how an election might play out. On balance, however, polling has good form for calling most races right – and is becoming increasingly accurate. If this comes as a surprise, it might be because humans often process negative memories (poll misses) more thoroughly than they do positive (accurate polls). Perhaps conscious that history may repeat itself, betting markets are ranking a Trump victory as more likely than what our model and the models of other outlets forecast.
In the US, the antipathy towards polling is heightened because they have a president most polls did not see coming. In 2016, survey data understated Trump’s margin against Hillary Clinton by between 3pts and 6pts in most key battleground states. Some of this miss could be attributed to margin of error, but for polls to have underestimated Trump in a uniform way across different states indicates something else was going on; and, in particular, that the pollsters struggled to correctly quantify insurgent movements.
The question for 2020 is: will it happen again? Polling this time has been much more stable. But intense uncertainty remains about their value and accuracy. Especially when it comes to whether there is a shy Trump vote.