See sourceSOURCES: National Election Study (Center for Political Studies, University of Michigan, 1952-2012); National Election Study Cumulative File (Center for Political Studies, University of Michigan, 2005); 2008 National Election Study (Center for Political Studies, University of Michigan, 2008); 2012 National Election Study (Center for Political Studies, University of Michigan, 2012.); and 2020 National Election Study (Center for Political Studies, University of Michigan, 2020).