Trump is not on the ballot, and the midterms will really come down to individual races, pedigree and district leanings. That being said, the stupid party as individual members have dug a huge hole for themselves. Failures all the way around except for the tax cut. Votes for the democrats dream budget, failure to eliminate Obamacare, no action on appointees, constant carping on national priorities like the wall. Major traitors within the party that match Maxine and Nancy in hatred for Americans. Why the hell would anyone vote for a congressional republican at this point.
Baring major indictments of democrats and their allies, Republicans, on an individual basis could get crushed. And this despite years of redistricting to improve their district voter configuration.