The relationship between religiosity and party identification in the U.S. has been both constant across time and most demographic groups within the population, including age, gender, region, and socio-economic status. Within each category of these groups, Americans who are the most religious are the most likely to be Republican, while those who are the least religious are the most likely to be Democratic.
The one exception to the basic religiousness and party identification relationship occurs among black Americans, who tend to be the most Democratic of any major race and ethnic group measured. Blacks are very religious on average, but the political orientation of blacks who are nonreligious does not vary significantly from those who are very religious. Democratic affiliation among black Americans hovers near 75% within all three religious groups of black Americans.
On the other hand, non-Hispanic whites, Hispanics, and Asians follow the basic pattern bserved in the general population, with more religious members of each group skewing more Republican. The relationship is most pronounced among non-Hispanic whites, among whom the swing in the net Democratic advantage goes from +18 points among those who are unreligious to -39 points among those who are very religious.