"Across the country, Democratic House districts have an average per capita income of $27,893. That's about $1,000 higher than the average income in Republican districts. The difference is relatively small because Democrats also represent a lot of poor districts, putting the average in the middle."

That income level is not considered "rich". As for presidential races: "In the election, Romney carried only one income group: people making $100,000 or more, according to exit polls."

You may also want to look at the money Republicans have raised for the presidential race including super PACs. Republicans have a much larger war chest due to large contributions from many very rich people.