The mistake you and the pollsters are making is to ignore the fact that the record high levels of voter enthusiasm are coming entirely from the right. Democratic enthusiasm is typical for a mid-term election. Republican enthusiasm, however, is unusually high.
Polls are failing to take this into account.
If this were a Presidential election year, both left and right wing voters would be turning out in high numbers and voter enthusiasm would not really matter. If 90% of your voters are going to vote anyway, it is very difficult for "enthusiasm" to close a 7% gap. However, this is not a Presidential election year and turnout will be considerably lower than it was in 2016. Higher enthusiasm levels could easily spur 60% of Republicans to vote instead of the 50% (or whatever the number is) that would otherwise head to the polls, and pffft! As quick as that, the 7-point advantage leftists think they have will be gone.
We'll see if that happens.
If the Democrats don't do as well on Tuesday as the polls predict, this is going to be why.
Watch out. You may be in for an unpleasant surprise.