According to that poll, the only shifts from 2016 (comparing Hillary-Trump vs D-R now) are among uneducated white people. every other group is roughly the same as in 2016. according to the poll, they are 8 points more D than in 2016
which, granted, are about 45% of the electorate and even more heavily concentrated in many of the swing senate seats
The D demographics, even if the margin doesn't change among them, should represent a bigger share of the electorate and thus shift the country left anyway. Combine that with a shift to dems among WWC with lower turnout from them and you've got yourself a wave