Population Density as a Predictor of Political Philosophy

Yesterday I posted some thoughts on  the geography of conservatism and liberalism in the United States. I included the following map:

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Compare that  map with the following map of population density:

Population Density 2007

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It seems rather clear that the higher the population density, the less conservative and more progressive the region.

The states with the highest density are (most dense first): New Jersey, Rhode Island, Massachusetts, Delaware, New York, Florida, Ohio and Pennsylvania. None of them has above average portion of conservatives. These states (with the exception of Pennsylvania and Florida) are core progressive states. (We generally think of their big cities as voting Democratic,)

The west coast progressive states are relatively large, and have regions of both high and low population density, but their urban metropolitan districts are large and the progressive urban populations outnumber the rural conservatives.

It would seem that there is something about the culture of high population density regions that correlates with progressive population. These are also regions with relatively high income, relatively high portions of people with college degrees, high portions of the population in managerial or creative industries, and more diverse populations. These are perhaps all implicated in producing a culture that votes progressive.