The 2018 midterm election was not resounding win for the D’s!
Historically, the incumbent president does take a hit in the midterm election. It was expected the R’s would lose something.
If 10% of the 50% who usually don’t vote found Mr. Trump so deplorable, they would have made a trip to the polls to cast a vote against him. The Senate should have flipped as some of those seats were not resounding R victories. But the non-voters stayed home in 2018. If they stay home in 2020, get used to another four years of Mr. T.