The last time a Democrat won a US Senate Race in/Republican won a US Senate Race in

States that currently have 2 Republican US Senators.
AK- Begich-D. 2008
AR- Pryor-D- 2008
FL- Nelson-D- 2012
GA- Miller-D- 2000
ID- Church-D- 1974
IN- Donnelly-D- 2012
IA- Harkin-D- 2008
KS- McGill-D- 1932
KY- Ford-D- 1992
LA- Landrieu-D 2008
MS- Stennis-D 1982
MO- McCaskill-D 2012
NE- Nelson-D 2006
NC- Hagan-D 2008
ND- Heitkamp-D 2012
OK- Boren-D 1990
SC- Hollings-D 1998
SD- Johnson-D 2008
TN- Gore-D 1990
TX- Bentsen-D 1988
UT- Moss-D 1970
WY- McGee-D 1970

States that currently have 2 Democratic US Senators.
CA- Wilson-R 1988
CT- Weicker-R 1982
DE- Roth-R 1994
HI- Fong-R 1970
IL- Kirk-R 2010
MD- Mathias-R 1980
MA- Brown-R 2010
MI- Abraham-R 1994
MN- Coleman-R 2002
NV- Heller-R 2012
NH- Ayotte-R 2010
NJ- Case-R 1972
NM- Domenici-R 2002
NY- D'Amato-R 1992
OR- Smith-R 2002
RI- Chafee-R 2000
VT- Jeffords-R 2000
VA- Warner-R 2002
WA- Gorton-R 1994

States that currently have 1 Democratic and 1 Republican US Senator could have 2 Democratic US Senators.
AZ- Sinema-D and Kelly-D
CO- Bennet-D and Johnston-D
ME- King-I/D and Gideon-D
MT- Tester-D and Collins-D
PA- Casey jr-D and Lamb-D
WI- Baldwin-D and Pocan-D