Richest/Poorest Congressional Districts

[Linus Van Pelt]

Has anyone ever seen/done an examination of the relationship between income and vote across all CD's? It's doesn't seem at all obvious what the graph would look like - my general understanding of the situation is that within pretty much every region of the country (except maybe the west coast), the richer areas are more R and the poorer areas more D, but that D regions overall are richer than R regions overall.