So I got linked to a very interesting and free online book, called
The Authoritarians. It's written by Bob Altemeyer up at the University of Manitoba, and he's a psychologist. The book is basically a summary of ~20 years worth of social sciences research, with what looks like quite a lot of solid data. I have some reservations (particularly with the classifications of odd-balls like myself), but all-in-all, it's highly recommended to look at. Because, while I may not agree entirely with his conclusions, the data he presents appears to be very solid.
There's also a criticism from John Martin in
Political Psychology and a response-to-the-response which Dr. Altemeyer e-mailed me by request. I'll put up a link to it if he gives me permission, otherwise I encourage you to e-mail him to request it yourself.
Basically, he's identified two cohesive personality groups, that he classifies as 'authoritarian followers' and 'authoritarian leaders' and has some very interesting information about how, in his (North American) surveys, those personality traits correlate with political & religious opinion. Speaking as a religious conservative with a preference for the Republicans over the Democrats, I'm not exactly happy with his results or conclusions, but the evidence he presents is very strong.
I encourage you to take a look.