In this study, I investigate the relationship between campaign contributions and legislative behavior of members of U.S. Congress (MCs) between 1980 and 2016. In the last four decades, political donations have become increasingly concentrated and economic inequality has reached the highest level of Western democracies. Contrary to expectations of a strong impact of money in politics, the literature has generally found mixed results for campaign contributions. In this sense, I analyze the relationship between the concentration of donations and three legislative activities of MCs: sponsorship of bills, speechmaking on the floor and witness appearances before committees. I find that the concentration of donations negatively correlates with all three endeavours. The interpretation of this result is that a very skewed structure of political funds makes a legislator more dependent from a relatively smaller number of donors and thus less responsive to the interests of voters. Overall, these findings represent the first empirical assessment of negative agenda power of interest groups and individuals giving large donations. Moreover, for bills the negative correlation is stronger for topics related to redistribution, especially health and housing policy proposals. This complex mechanism of influence of campaign contributions could have ultimately limited Congressional discussion of issues related to economic inequality. The results of this study show that the current system of campaign contributions distorts MCs’ incentives for the representation of their constituencies.