My friend, former colleague and co-author Rob Griffin nails it in this Post Monkey Cage piece. Read it and shake your head sadly. Ah what fools we mortals be....
Note: NEP is the National Election Pool, the nom de guerre of the exit polls.
"[T]he NEP’s estimates of who voted — what percentage of voters fall into any given demographic group — appear to be wrong. This kind of problem has plagued the NEP in the past and, apparently, it is an issue again this year. If the NEP’s estimate of who voted is incorrect, then the vote margins — the percent by which each demographic group voted for each candidate — could be incorrect. That can distort our picture of how different groups voted. And if the numbers for how different groups voted Trump/Biden are wrong, they shouldn’t be used to try to explain what happened in this election.
This year the NEP suggests that just 65 percent of voters were White and 34 percent were White without a four-year college degree. These estimates are dramatically smaller than what other research has found during prior elections. For example, the States of Change project — a series of reports that I co-authored with Ruy Teixeira and Bill Frey — found that 74 percent of voters were White in 2016, and 44 percent were White non-college. These estimates are identical to the Pew Research Center’s analysis of a large voter-validated survey.
What can that tell us about this year’s voters? We know that the relative turnout of different groups does not typically change dramatically between elections. If the relative turnout rates of different groups stayed the same, long-term demographic trends would lead us to expect 72 percent of 2020 voters to be White and 41 percent to be Whites without a college degree. For the NEP’s estimates of 65 and 34 percent to be correct, the relative turnout rates of different racial groups would have to have changed substantially and in ways that are not believable.....
I find that the NEP implies that 66 percent of White Americans turned out in the last election. This is just barely higher than the implied turnout rates of Hispanic Americans (63 percent) and notably lower than the implied turnout rate of Americans who are Asian or belong to another racial and ethnic group (74 percent). That’s out of line with the U.S. Census Bureau’s Current Population Survey, widely considered to be one of the best sources of information about the U.S. electorate. The CPS has consistently shown that White citizens cast ballots at rates higher than those groups."