I am sorry if you were hoping I'd be writing a rare political essay. I just am not that interested in politics, but the history and sociological aspects do fascinate me. As such, this is more of a sociological speculation about one aspect of American political history.
The most recent thing to catch my attention is an image floating around on the web that shows a comparison of the 2012 Presidential election results with the 1846 map of U.S. states that supported slavery.
The states that voted Republican/conservative in the 2012 Presidential election are nearly identical to all the states that supported slavery. Meanwhile, all the states that voted Democrat/liberal are all the progressive states that mirror those states which abolished slavery.
Now there are many political economic, and sociological factors that play into this, but the question I have, is how much of a coincidence is it really? I would be tempted to say this is an odd coincidence if it were a coincidence. However, I don't think it is a coincidence.
Following Jared Diamond's biogeographical/border theory, and Taking a Guns, Germs, and Steel approach, I would say it's not that much of a coincidence at all. All the blue states and free states are basically bordering the ocean and/or foreign cities/countries. This means two things: trade and cultural exchange.
Trade and cultural exchange means there is a steady flow of ideas, different ways of thinking, different cultural norms, and the need for foreign relations and diplomacy when dealing with other cultures. In other words there very location demands they be more open minded. Constant trade equates to a strong economy and more wealth. If they were not open minded, then trade would grow difficult, perhaps even cease, all the importation of new ideas would halt, and their contact with other cultures and ways of thinking would be greatly diminished.
Being constantly bombarded by new ideas, however, is one way in which we gain knowledge. It also helps us gain perspective as it allows us new ways in which to question our own preconceived notions. So it's no surprise that these areas lean toward the liberal side of the political spectrum. Liberals are generally more cultured, and studies have shown liberals are traditionally better educated too, and I suspect this might be one of the major factors as to why.
Another thing to realize is, although the southern states border Mexico, which is a foreign country, historically speaking there has been an artificial barrier preventing fluid cultural exchange. This is what Jared Diamond calls a history of division by borders.
He points to a similar situation that occurred along the border of Haiti and the Dominican Republic. One side flourished, due to various biogeographical circumstances as well as a steady stream of historical events, and the other side turned into a virtual wasteland. Diamond's hypothesis is mirrored by what has been happening along the Mexican/American boarder ever since we got California back from Mexico in 1847.
The diffusion of culture, as well as ideas and new knowledge, impacts these border towns and port towns more freely--except where the border is too well built up. It takes time for these ideas to permeate further in-land, especially when population density thins. Additionally, if you have a large insurmountable wall built up along your borders (or borders so vast that no wall is necessary) which is intended for keeping others out, this will be a point of tension, as well as frequent friction, and will likely halt the influx of different people, cultural worldviews, and ideas.
Thus the liberal mindset will shift toward a more conservative one. Blue becomes red under specific conditions just as red will become blue under other conditions.
This explains why all up and down the U.S. coast we tend to find blue. We find blue in the populated areas of our country which border the populated areas of Canada. A country with whom our borders are lax and our policies friendly. Trade can carry on relatively unhindered and there is nothing causing friction and nothing preventing those ideas and cultures from intermingling.
Mexico, on the other hand, faces rigid borders and rather unfriendly policies with regard to immigration. As such, this helps explain why these regions lack multiculturalism of the more open styled borders between nations.
Additionally, as I hinted at above, large land masses like that stretching across Idaho, Montana, North Dakota, which have small populations with even smaller population densities, and don't border any major Canadian cities, tend to be landlocked. The border is natural instead of man-made, but the effect is the same. Less culture, alternative ideas, and different forms of knowledge make its way into these landlocked regions. Multiculturalism fades, and again the shift from blue to red, liberal to conservative, can be seen.
At any rate, I thought this image was fascinating, and felt like writing down my thoughts while they came to me. What I propose isn't in anyway certain, but it seems highly likely, given the circumstances. Feel free to let me know what you think in the comments section down below.