[thaumasiotes]

> Polls have more impact if they are more representative of statewide turnout among demographic things he chose like “black” and “low income.” This is why his predictions were so accurate for Obama’s 2008 and 2012 elections

I find this argument strange, because black turnout was unusually high in 2008. That should have a negative impact on the accuracy of statistical adjustments, not a positive one.

[an_opabinia]

I think he made an estimate for the increase in black turnout. If I were designing the model, and I believed turnout is the biggest factor (maybe inconclusive among political scientists), I would look at the circumstances where turnout changes based on candidate's demographics and validate it across statewide and congressional races.

However, we will never know, because they never published the code.

[wtallis]

> I think he made an estimate for the increase in black turnout.

I think that kind of adjustment is usually the responsibility of the pollsters, with their likely voter models. I don't think FiveThirtyEight directly tries to also apply such an adjustment, because that would be at serious risk of overcorrecting.

Similarly, this year many pollsters have added level of education as a factor to their demographic weighting, to address a shortcoming in their 2016 performance. FiveThirtyEight consumes those poll numbers without adding their own layer of demographic adjustment.