As FiveThirtyEight has evolved over the past 10 years, we’ve taken an increasingly “macro” view of polling. By that, I mean: We’re more interested in how the polls are doing overall — and in broad trends within the polling industry — and less in how individual polls or pollsters are performing. …
Still, in election coverage, the “micro” matters too, and our newly updated pollster ratings — in which we evaluate the performance of individual polling firms based on their methodology and past accuracy — are still a foundational part of FiveThirtyEight. …
So which pollsters have been most accurate in recent elections? Because some races are easier to poll than others, we created a statistic called Advanced Plus-Minus to evaluate pollster performance. CONT.
Nate Silver, FiveThirtyEight