There’s a lot of talk right now that polling failed. But Trump’s win was hardly an unpredictable “black swan” event. All the evidence was there, if you knew how to read it.
In fact, the polls did ok, 2016 was not even a particularly large miss by historical standards. …
Yet the most optimistic predictions gave Clinton a 90 percent chance, because they missed a fundamental fact: polling errors tend to affect many states at once, and in the same direction. CONT.
Jonathan Stray, Quartz