ASH asked an question: 为什么红州基本上都是些落后的州?
It is an interesting academic question, some people must have or should have written a PHD thesis about it.

There is a theory (I forgot the source, sorry): Liberalism rely on taking other people's money to fund its social engineering (or utopia). In poor country, it takes the form of communist revolution like red China, USSR, etc. In countries where communists fail, liberalism grows only when the country (state) become richer so there are other-people's-money to take/tax. The more money it takes, the liberalism spread more and getting more widespread until (perhaps) someday those "other-people's-money" are taken to a point the system collapse under its own weight.

Poor country (state) simply can't afford liberalism. Who are they going to tax there?

The theory is certainly debatable but that's the most plausible-sounding theory I read. It appears countries like Greece are getting near the breaking point.

Any other theories?