John Quiggin:
"Southern White" as an ethnicity: The best way to understand the distinctive characteristics of US voting patterns is to to treat "Southern White" as an ethnicity, like Hispanic.... Each of the major parties becomes an coalition between a solid bloc vote from an ethnic minority and around half the votes of the non-Southern white ethnic majority, which is more likely to vote on class lines. The question then is which ethnic/class coalition is bigger. As in other countries, voting for the more rightwing party is correlated, though not perfectly with higher incomes and (conditional on income) lower education, and to shift according to broader ideological movements.... [T]he demographic trends are favorable [to the Democratic Party]. The ethnic population balance is shifting from White Southerners to Blacks, Hispanics and Asians. So, as long as this alignment remains stable and the Democrats continue to gain ground with younger voters in general, the odds shift in their favor... unless the Rs manage to revive a new, improved version of Jim Crow. A demographic swing can't benefit the other party if that demographic can be kept from voting.