In his recent volume, Affluence and Influence: Economic Inequality and Political Power in America, political scientist Martin Gilens provides conclusive evidence that national policymakers are much more responsive to the policy preferences of the affluent than the middle class or the poor. In fact, this relationship is so strong that when the preferences of the middle and lower classes diverge from those of the wealthy, there is almost no correlation between policy outcomes and the desires of these less advantaged groups.
While conducting this research, Gilens developed a dataset of over 2,000 survey questions about specific proposed policy changes (1964-2006). The policy preferences explored in the dataset range from raising the minimum wage to restrictions on abortion to sending troops to Bosnia. The degree of support for each of these proposed changes expressed by individuals in different income groups was then related to the subsequent policy outcomes. You can access the data used in Gilens' research on this page in both SPSS and STATA formats.