Wonder why the GOP only can resonate with morons these days

They've gone far enough to the authoritarian side that they're hitting what these studies reference. This snippet from one says it best:

Right-wing ideologies offer well-structured and ordered views about society that preserve traditional societal conventions and norms (e.g., Jost, Glaser, Kruglanski, & Sulloway, 2003). Such ideological belief systems are particularly attractive to individuals who are strongly motivated to avoid uncertainty and ambiguity in preference for simplicity and predictability (Jost et al., 2003; Roets & Van Hiel, 2011). Theoretically, individuals with lower mental abilities should be attracted by right-wing social-cultural ideologies because they minimize complexity and increase perceived control (Heaven, Ciarrochi, & Leeson, 2011; Stankov, 2009). Conversely, individuals with greater cognitive skills are better positioned to understand changing and dynamic societal contexts, which should facilitate open-minded, relatively left-leaning attitudes (Deary et al., 2008a; Heaven et al., 2011; McCourt, Bouchard, Lykken, Tellegen, & Keyes, 1999). Lower cognitive abilities therefore draw people to strategies and ideologies that emphasize what is presently known and considered acceptable to make sense and impose order over their environment. Resistance to social change and the preservation of the status quo regarding societal traditions—key principles underpinning right-wing social-cultural ideologies—should be particularly appealing to those wishing to avoid uncertainty and threat.

Indeed, the empirical literature reveals negative relations between cognitive abilities and right-wing social-cultural attitudes, including right-wing authoritarian (e.g., Keiller, 2010; McCourt et al., 1999), socially conservative (e.g., Stankov, 2009; Van Hiel et al., 2010), and religious attitudes (e.g., Zuckerman, Silberman, & Hall, 2013).