Political scientist, Andrew Gelman has some great graphs on the connection between economics and ideology. Comparing income levels, ideology and party idenitification, he and collaborator Daniel Lee found the connection between income and party identification was strongest among conservative Republicans. But the relationship was "close to zero" for liberals. Liberal Dems were spread across all income groups, while conservative Dems had much lower income levels.

My reading is that class continues to play a considerable role in American politics:  With the exception of liberal Dems who draw from across the spectrum of classes, the parties and their key factions increasingly represent class blocs. Gelman notes that the connection between economic status and party/ideology underpins America's increasingly polarized policy debates. He's right.  In the current zero-sum economic climate, it's only likely to get worse.