Steven Pinker takes a crack at explaining the red state - blue state map:
But while these theories help explain why the seemingly diverse convictions within the right-wing and left-wing mind-sets hang together, they don’t explain why they are tied to geography. The historian David Hackett Fischer traces the divide back to the British settlers of colonial America. The North was largely settled by English farmers, the inland South by Scots-Irish herders. Anthropologists have long noted that societies that herd livestock in rugged terrain tend to develop a “culture of honor.” Since their wealth has feet and can be stolen in an eye blink, they are forced to deter rustlers by cultivating a hair-trigger for violent retaliation against any trespass or insult that probes their resolve. Farmers can afford to be less belligerent because it is harder to steal their land out from under them, particularly in territories within the reach of law enforcement. As the settlers moved westward, they took their respective cultures with them. The psychologist Richard Nisbett has shown that Southerners today continue to manifest a culture of honor which legitimizes violent retaliation. ... Admittedly, it’s hard to believe that today’s Southerners and Westerners carry a cultural memory of sheepherding ancestors. But it may not be the herding profession itself that nurtures a culture of honor so much as living in anarchy.
You can't talk about why the South today has a lot of white solidarity centering around the Republican Party and the North does not without talking about the, uh, Canadian border.
Pinker's Massachusetts is 6 percent black, so what's the worst that could happen if the Democrats control the statehouse? A bunch of white Democratic politicians will just steal billions more on the next Big Dig. But, eventually, it will get dug. Every so often the white people of Massachusetts elect a Mitt Romney to cut down on the thieving by white Democrats, but it's really not that big of a deal.
Mississippi is 37 percent black, so what's the worst that could happen if the Democrats control the statehouse? Well, blacks will make up the majority of the Democrats, so ... Detroit, Gary, East St. Louis. Not surprisingly, almost all the white people in Mississippi make sure to vote Republican.
You can see the same white solidarity in liberal cities like New York and Chicago in mayor's races. Blacks went one and done in the New York's mayor's office and the Democrats are 0 for 5 in NYC ever since. But New Yorkers will vote overwhelmingly for Obama next month because that's not a real important job like Mayor is, so they can afford to make symbolic gestures of racial enlightenment at the national level.
(Something that's worth bringing up here is that for a few decades now, better educated blacks have been voting with their feet to move away from liberal Northern states to the white-run state of Georgia. That was background for Tom Wolfe's 1990s Atlanta book A Man in Full. Blacks get a small city to run at the center of a vast white-dominated conurbation in a Republican-dominated state, and despite not unexpected problems, the system works fairly well. There's a general pattern that white conservative states like Georgia and Texas tend to be better for blacks and Latinos than white liberal states, which is, in the long run, a very big problem for Republicans: when Republicans are successful at doing what they want to do, such as encouraging building jobs and houses, their success attracts non-Republicans.)
Anyway, there are other reasons red states are red and blue states are blue, as well, such as the dirt gap. A large number of red states are in the upper Louisiana Purchase and surrounding areas and are mostly white. Some are extremely orderly and nonviolent, such as Utah, and others are not. Land availability is the big issue driving them red.