Despite the common assertions that religious and cultural conflicts are increasingly dominating American politics, there is quite a bit of data showing that income still correlates very strongly with voting patterns in about the way you'd predict, with wealthier voters more likely to vote Republican and working class voters more likely to vote for Democrats. (See, for example, Nolan McCarty et al., Polarized America (2006)) A couple of Cornell professors have recently published an interesting paper trying to parse the impacts of religion and income on voting patterns over the past few elections. They find that religious conservatism has increasingly manifested itself as political conservatism, but most markedly among those with family incomes of more than $75,000. You can download the paper here. There are some problems with the way they measure religious conservatism, particularly as it relates to Catholics. Specifically, their measure of religious conservatism is based on a set of questions about biblical authority. While I think this works well for distinguishing among types of Protestants, it works less well among Catholics, since the main axes of disagreement among Catholics do not tend to relate to Biblical authority. Still, even using that metric, they find the same pattern among Catholics. It's interesting to think about the reasons for this.