Confused as to why the U.S. Senate has snapped into action to prevent sequestration-induced flight delays but has done nothing for low-income families losing their Section 8 vouchers or slots in day care programs? Wondering why FAA flight controllers are more important than teachers on Native American reservations? Well, this chart from Larry Bartels' 2005 paper on "Economic Inequality and Political Representation" tells you what you need to know.
What Bartels did was look at public opinion views of people in the bottom third, the middle third, and the top third of the income distribution. Then he looked at how well senators' votes match the opinions of their constituents. He finds that both Democrats and Republicans do a fair amount to try to align their views with those of their middle-income constituents. Democrats respond to their high-income constituents about as strongly as they do to their middle-income ones. Republicans are very responsive to their rich constituents. And neither party cares what poor people think.
So it turns out that when Congress cuts domestic discretionary spending "across the board," it doesn't really cut it across the board. A program that's important to prosperous frequent travelers gets spared the ax.