By 2012, 69 percent of white voters who reported attending religious services at least once per week identified with the Republican Party compared with only 41 percent of white voters who reported rarely or never attending religious services—the largest divide ever recorded. Some 75 percent of religiously observant whites voted for Mitt Romney in 2012 compared with only 46 percent of non-observant whites.

Much attention has been paid by political commentators to the potential impact of growing income inequality on partisan polarization. When it comes to explaining partisan polarization in the contemporary American electorate, however, income differences appear to play a much smaller role than either race or religion. According to data from the American National Election Study, the correlation between family income and party identification among all voters in 2012 was a very modest 0.13. As family income goes up, voters are a bit more likely to back the Republicans, but not strongly so. The correlation among white voters was meager and statistically insignificant 0.03.

As the figure below shows, at every level of family income, religiously observant whites were much more likely to vote for the Republican presidential candidate in 2012 than non-observant whites. In fact, non-observant, upper-income whites were much more likely to vote Democratic than religiously observant lower-income whites. Indeed, family income had no relationship at all with vote choice among religiously observant whites. A remarkable 80 percent of observant whites with family incomes below $15,000 voted for a Republican presidential candidate who famously expressed no interest in appealing to 47 percent of the electorate including, presumably, those living below the poverty line.