MN would be tough to crack.
One overlooked state is MA. If widely popular Baker jumps in, then Warren could be in trouble.
Another blue state that could be in trouble is MD if Hogan jumps in, although I doubt he will.
I don't think AZ will be in play at all. NV is the only GOP state I think we could lose.
States that I think are gone for dems;
ND, MT, MO, and IN
Tossup;
FL, OH, PA, WI, MI, and NV.
WV is special in that it depends if Manchin runs as a dem or republican. If he stays dem, then the seat is lean D.
Everything else is lean or solid towards the incumbent party.