Yep. I suggest following Ballotpedia's updates on the primaries, they've been saying this for the last few months now. Pro-Trump Republicans are winning primaries and in several hotly contested primaries none of the candidates actually opposed Trump. Meanwhile, Republican primary turn-out is higher then that of the Democrats and that could predict a low turn-out for Democratic voters during the General.
Take the Arizone US Senate seat, for example. It has been rated the most likely Senate Seat to flip during the 2018. McSally, the party-supported candidate and poll-favorite used to be critical of Trump in 2016 but has completely 180-degree-turned, and her two opponents are completely aligned with the Trump administration. They are all running on a pro-Trump/Administration platform, in a very unsafe seat, in a midterm election. Honestly, if the Democrats don't take this seat, they might as well stop trying.
The Democrats are still in a good position to take back the House, but with the Senate is unlikely to flip, the effects of that are really limited. If they fail, you might as well re-name the Republican Party the Trump Party and I'm willing to bet Trump will be almost ensured the Republican nomination for 2020.