Conventional wisdom attributes the rise of Evangelical activists in the Republican Party to mobilization efforts undertaken by Christian Right organizations (Conger 2009; Green et al. 1996; Kohut et al. 2000; Layman 2001; 2010; Oldfield 1996; Rozell and Wilcox 1996; 1997; Smidt and Penning 1997; Smidt 2013; Wilcox and Larson 2006). Likewise, the rise of Secular activists in the Democratic Party is attributed to mobilization inspired by a backlash against the religious tenor of conservative politics (Bolce and De Maio 1999a; 1999b; 2002;Hansen 2011). However, the efforts of Christian Right organizations and reactions to those efforts on the political left occurred alongside major shifts in the religious affiliations of Americans. In other words, the rise of Evangelical activists on the right and the rise of Secular activists on the leftmay have more to do with those groups being fruitful and multiplying than with mobilization and culture wars. Therefore, disentangling the role of political mobilization from the role played by demographic forces is an essential part of understanding and interpreting changes in the composition of partisan activists. In what follows, the basic trends are examined and then the method described in Chapter 3 is used to conduct an analysis motivated by the counterfactual, “How much composition change would occur in the activist pools if basic demographic forces were the only forces shaping changes in the activist pools?” The counterfactual analyses reveal that demographic shifts play a much more important role shaping the activist pools than has been previously recognized.

In light of the importance of demographic changes in the religious affiliations of the American public, the sources of those shifts are also examined. There is an academic debate regarding the best way to explain the changing religious landscape in the United States. On the one hand, Hout et al. (2001) and Wuthnow (2007) credit birth rates and marriage patterns with the rise in the number of Secular identifiers.