Democrats guide to regaining control of the US Senate in 2020 or 2022 is.
2020- win all of the Democratic held US Senate seats up in 2020 except AL(Jones-D), win 4 or 5 Republican held US Senate seats up in 2020 depending on whether Democrats win the 2020 US Presidential Election.
Republican held US Senate seats up in 2020 Democrats are favored to win are:
CO(Gardner-R vs Hickenlooper-D)
AZ special(McSally-R vs Kelly-D)
NC(Tillis-R vs Cunningham-D)
Democrats need to win one or both of the GA US Senate seats up in 2020, IA, KS- if Kobach-R is the Republican Nominee, and/or ME.
2022- If a Democrat is POTUS,
Hold onto every Democratic held US Senate seats up in 2022 including AZ(Kelly-D)
CA,CO,HI,IL,MD,NV,NH,NY,OR,VT,and WA are in the lean,likely and safe Democratic column.
Pick up NC(OPEN-Burr-R), PA(Toomey-R) and/or WI(OPEN Johnson-R)