There were 23 Democrat Senate seats up this year, compared to only 8 Republican seats. They actually did pretty well to only lose 2 or 3 net, depending how many they are able to steal in the next week of recounts.
In 2020, there are 22 Republican Senate seats up, and only 12 Democrat seats. 2020 is going to be a very tough year and Trump is going to need some big coattails to hold the Senate.
Don't senators run every 6 yrs? He might remain unaffected. It's whoever runs in 2024.
When all the recounting is done, the republicans will only be at a net +1.