[Professor S]

1) We care a two party system, so parties must have a big umbrella, unlike in a parliament where there are many parties that can be very specific. Then "governments" are created by the winning party from a series of those parties. In that sense, you could say that the American system is two governments running against each other, rather than two parties.

2) Unlike many like to say, I don't think Republicans didn't gain the south by appealing to racists, they appealed to the south by appealing to evangelicals (and no, they are not necessarily the same thing). Reagan likely would have not won the election without the "moral majority" consisting of a network of religious groups. To a fiscal conservative, this was a necessary evil at the time, but over the decades the social conservatives seem to have taken over. Part of the dumbing down of America on both sides of the political spectrum.

3) IMO, many voters who put social progressiveness at the forefront link it directly with economic progressiveness/redistribution of wealth/picking winners and losers, or view them as one and the same. It comes from a string sense of social justice, a.k.a. "fairness". "It's not fair that gay people can't get married and it's not fair that everyone can't have the same healthcare plan."

4) Fiscal conservativism doesn't sound nice or fair, even if we believe it is inevitably the most kind, fair and overall effective economic policy. People like things that sound nice and fair... until the reality of that fairness and niceness smacks them in the face (i.e. Healthcare). Unfortunately, people vote for concepts and talking points, not details and comprehensive plans... but they scream about them in town hall meetings.