Paul Djupe and I wrote a piece for Five Thirty Eight today about how religion inhibits socialism in American party politics. We attribute this to two factors: values and mobilization. Using data from the Public Religion Research Institute, we find that socialist values are strong among those without religion (the Nones). But the problem is that Nones currently have fewer organizational resources to transfer values into politics. One big reason is that they do not go to church, the most widespread social organization in the U.S.
Here's our article: http://fivethirtyeight.com/features/americans-may-be-too-religious-to-embrace-socialism/