If the generic ballot is dead even just before the election, the Dems will still pick up lots of seats, and the House at a minimum, and maybe the Senate too, as well as Governors and state legislatures. The reason is illustrated by the special elections where Dems are flipping deep red seats. Dem turnout is very high. They have done a superb job of using fear to motivate their base. Trump supporting Republicans, Independents and Democrats are not turning out at the same level.
In VA, they also came up with some more high tech methods of identifying likely Dem voters and getting them out to vote - particularly young voters. They've probably done that in other races like Alabama. Once again they may be ahead there, like in 2012. I wonder if the RNC strategists took note. Probably not.