Why can moderate republicans win in red states but not the other way around?

[RI]

Plenty of Dems have won in "red" states since 2010: Nixon, Bullock, Donnelly, Heitkamp, McCaskill, Manchin, Bel Edwards, Beshear, Tomblin, Beebe...

[RI]

Because red states are becoming the equivalent of blue cities.

I noticed Hillary's share of the vote in Mingo county, WV dropped to 14%. A county that was going Dem as recently as the early 2000s.

Justice won Mingo by over 15 points. It's not out of reach for the right type of Democrat.

[RI]

If anything, the hardest states to topple for the opposing party are the polarized, inelastic, western, (mostly) vote-by-mail states: California, Idaho, Oregon, Utah, and Washington. States where the opposition party is relatively more moderate than nationally are the most likely to see opposition takeovers; if the GOP in New England was like the GOP in the South, they'd almost never win, and vice versa for West Virginia and the like. Out west, we see Dems are very liberal, even in conservative states (ex: Salt Lake City in Utah), and Republicans are very conservative, even in more liberal states.