This article by Steve Sailor (via Mickey Kaus) is will worth reading. Put simply, it explains the current American Red State/Blue State gap largely in terms of self selection and children. It’s much more expensive to have children in a blue (Democratic) state compared to a red (Republican) State. Throw in some freedom of movement and self selection and you’ve got a bifurcated America.
A few quibbles. He seems to throw in Atlanta as a “Red City” which is very much not the case. While metro Atlanta is a very red metro area, the city itself is quite blue. Also, the areas with the most recent and illegal immigrants (here in the Atlanta metro area anyway) seem to be the most Republican areas, which is seemingly at odds with his theory.
He also does not mention the Roe Effect, payroll taxes, the total tax burden, the actual cost of a mortgage (I got the full spiel from my mortgage broker when I refinanced, the cost of the mortgage itself can really vary quite a bit.)
On the whole, well worth reading though.