US Senate seats Democrats will win in 2020 to have majority control of the US Senate in 2020.

US Senate seats up for re-election in 2020 that are Safe Democratic.
1)RI(Reed-D)36
2)MA(Markey-D or Kennedy-D)37
3)NJ(Booker-D)38
4)DE(Coons-D)39
5)OR(Merkley-D)40
6)IL(Durbin-D)41
7)VA(Warner-D)42
8)NM(Lujan-D)43
US Senate seats up for re-election in 2020 that are Likely Democratic
9)MN(Smith-D)44
10)NH(Shaheen-D)45
US Senate seats up for re-election in 2020 that are Lean Democratic
11)MI(Peters-D)46
12)CO(Hickenlooper-D)47
US Senate seats up for re-election in 2020 that are Tilt Democratic
13)AZ special(Kelly-D)48
14)NC(Cunningham-D)49
To get majority control of the US Senate in 2020, Democrats need to win the 2020 US Presidential Electoral College vote and:
ME(Gideon-D),IA(Greenfield-D),GA special(Tarver-D),GA regular(Tomlinson-D), or KS(Bollier-D vs Kobach-R)
Winning both of the GA US Senate seats in 2020 will definitely give Democrats majority control in the US Senate in 2020.