Disbelief in evolution is the best indicator of stupidity. It doesn’t matter if you were born stupid or every adult in your community is a moron who gave you bad information which made you stupid. Anyway, Republicans are getting more stupid at a fairly rapid pace, while Democrats are getting less stupid at a slower pace.
What’s probably happening is that anyone with half a brain is leaving their evangelical hamlet and moving somewhere where people eat quiche and drive Volvos.