There are dynamics for Democrat gains this year. That’s the norm in an off year election. That said tha should not be a wave election. The economic news plus a president in a normal range of popularity should mean both sides have good turnout. Our voters need to be motivated and our party needs to run some effective ads that battle the media narrative.
I think a big mistake a lot of R’s may make is to think that Trump has much in the way of coat tails. I think most of the voters see him not as a republican, but an independent that simply chose a party afiliation to get elected. i.e. he can be wildly popular, but neither party benefits from it unless the particular candidate is a lot like trump in his public perspective.
I guess we’ll see, though.