CNBC's John Harwood has a column based on Brookings Institution analysis:
the two parties now speak for dramatically different segments of the American economy....districts won by Democrats account for 61 percent of America's gross domestic product, districts won by Republicans 38 percent.
Says Brookings researcher Mark Muro: "The Democratic Party and Republican Party, at this point, really do occupy different economic worlds and represent different economic worlds."
Analysis by the Brookings Metropolitan Policy Program documents the gap between them. Residents of districts won by Democrats generate 22% more output per worker, and have a 15% higher median household income.