Please see below details of a report released by Juhem Navarro-Rivera, who has worked on a number of reports about the nonreligious, in conjunction with the Public Religion Research Institute on the connections between religion and politics in the US.  The report focuses on the nonreligious (a.k.a. religiously unaffiliated):

http://publicreligion.org/research/2012/10/american-values-survey-2012/