How not to “unskew” the polls

Corrections to inflexible partisan benchmarks usually fail

I wrote a couple a months ago about why I think the theoretical motivation behind “unskewing” the polls is completely fine, despite what you may hear from other analysts. People that attempt to de-bias the polls are simply asserting that most have too many Democrats or Republicans in them, pushing the industry to overestimate support for one candidate. Since we have plenty of evidence that polls with more Democrats in them in 2016 artificially inflated Hillary Clinton’s projected vote margins both nationally and (especially) in key states, it’s reasonable to try to “unskew.”

But the problem is not the idea of unskewing, it’s that it’s usually performed poorly. The practice of de-biasing the data consists of (1) figuring out how many Democrats or Republicans were sampled in a poll; (2) figuring out how many Democrats or Republicans there should have been for that geographic region; and (3) adjusting the poll numbers to what they would have been if they had the “correct” partisan composi…