that less-educated whites, who historically have had a low propensity to vote, turned out in greater numbers than pollsters predicted
because
In states where white voters tend to be well-educated, such as Colorado and Virginia, the polls pegged the final results perfectly. Conversely, in northern states that have lots of whites without a college degree, Mr Trump blew his polls away—including ones he is still expected to lose, but by a far smaller margin than expected, such as Minnesota.
and in this case I would expect social desirability bias to be stronger among well-educated (is there any research about that in general case?), because the percentage share of their peers that do not like Trump is greater.
Another possibility is that
because
and in this case I would expect social desirability bias to be stronger among well-educated (is there any research about that in general case?), because the percentage share of their peers that do not like Trump is greater.