There's been a bit of discussion about these maps showing how the 2004 presidential election vote would have been decided if only the poorest or wealthiest voters in each state had been counted.
But really, all the information is in these plots from the same study.
There is no red-blue divide among the poorest voters and little among middle class. It's a rich thing.
The wealthiest voters in the poorest states are hard-core Republicans, and there's a nearly linear correlation between the wealth of a state and the party affiliation of the wealthiest voters in that state. So for all the pundits and campaign managers trying to figure out the difference between salt-of-the-earth midwestern farmers and godless city-slickers, you're wasting your time with the wrong demographic.