Every state is winnable for both parties. If it wasn't for Larry Hogan, everyone would have Maryland on this list, but they have a Republican governor.
There is some validity to this. Wyoming, Oklahoma, Tennessee, and Arkansas all had Democratic governors as recently as 2010; only in this decade have they moved "beyond reach" for the Democrats. California and New York, likewise, had Republican governors during the last decade, and Chris Christie just left office in New Jersey a few years ago. But other states have had a much longer drought: Oregon hasn't elected a Republican governor since 1982, and South Dakota last elected a Democratic governor in 1974.
It's true that some states have had a longer drought, but that's just a coincidence. Oregon came pretty close to electing a Republican in 2018, and South Dakota almost elected a Democrat. There are enough examples of deep blue states electing republican governors and deep red states electing democratic governors that I am confident in saying it is possible everywhere.
