- Geographically very isolated from other population centers within the state. Would almost certainly have to be west of the Great Plains.
- Economically dominated by one or two "out-there" industries that would favor said party (e.g. marijuana farming and/or eco-tourism)
- Would have to be racially and religiously homogeneous (could be white, AIAN, NHPI, or mixed-race). There would need to be some sort of community cohesion beyond being super isolated that would make a strong perennial third-party presence sustainable.
Hot take--tbh I think only the last characteristic would need to be present. The equivalent of the first two which most readily springs to mind imo is the Golden Triangle in California, which votes firmly D.
I'm glancing at Humbolt and in 2016 Johnson and Stein did combine to get 9.7% of the vote with all third party candidates receiving 13.1% in total. California has one of the most third party friendly electoral systems so I could see state level candidates doing even better.
