Post-mortem analysis of the 2016 election found that a failure to adjust for overrepresentation of college graduates was among the reasons many state-level polls underestimated support for Donald Trump. Voters who graduated from a four-year college are more likely to answer surveys than other adults and, in recent years, they are also more likely to support a Democrat for president. If a battleground state poll does not adjust for having too many college graduates, it is at risk of overstating support for a Democratic presidential candidate (in this case, Joe Biden). CONT.
Nick Hatley & Courtney Kennedy, Pew Research Center