The question is whether the Senate can be flipped, and it depends on the POTUS candidate while holding the House. Turn-out must be by proportion more than in 2016 since the Electoral College requires certain swing states to be won by much larger margins in 2020.

year/Voting Age Population/Turnout/%VAP

2008	229,945,000	131,407,000	58.2%
2012	235,248,000	129,235,000	54.9%
2016	250,056,000	138,847,000	55.7%

en.wikipedia.org/…

Aside from the phenomenon of ticket-splitting the above chart is interesting in comparison to the analysis of flippable Senate seats.

Safe D	Likely D	Lean D	Tossup	Lean R	Likely R	Safe R
DE (Coons)	MN (Smith)	CO (Gardner)	AZ (McSally)	GA-A (Perdue)	AL (Jones)	AK (Sullivan)
IL (Durbin)	NH (Shaheen)	MI (Peters)		GA-B (Loeffler)	IA (Ernst)	AR (Cotton)
MA (Markey)				ME (Collins)	KS (OPEN)	ID (Risch)
NJ (Booker)				NC (Tillis)	TX (Cornyn)	KY (McConnell)
NM (OPEN)						LA (Cassidy)
OR (Merkley)						MS (Hyde-Smith)
RI (Reed)						MT (Daines)
VA (Warner)						NE (Sasse)
						OK (Inhofe)
						SC (Graham)
						SD (Rounds)
						TN (OPEN)

www.dailykos.com/…