It's not only the Presidential race --- let's take a look at the polls in the Tillis/Cunningham race in North Carolina. Tillis beat Cunningham by a good margin --- yet many polls in the recent days had Cunningham up by 5, 6, 8 , or 10 points. Well outside the margin of error.
https://projects.fivethirtyeight.com/polls/senate/north-carolina/
https://projects.fivethirtyeight.com/polls/senate/north-carolina/