In those states that conduct presidential preference primaries, there are usually some statutory candidate filing requirements, but these vary considerably from state to state. (politics.stackexchange.com)
So what does the modern presidential preference for Catholic and Jewish nominees say about our national politics? (religion.blogs.cnn.com)
Using the Daily Kos analysis of presidential preference by Congressional District, we can get actual 2012 results: (politics.stackexchange.com)