Concerns that democratic institutions are biased towards "special interests" and lobbyists are longstanding and span multiple countries. Since the opportunity cost of not getting involved in democratic policy-making is high, interest groups have a strong incentive to participate. Surprisingly, however, political economists have struggled to identify exactly how interest groups and lobbyists affect political outcomes. In this dissertation, I contribute to the literature on interest group influence by arguing for an alternative point of access to democratic institutions. Specifically, using the committee system in the U.S. Congress as a test case, I argue that interest groups work to "capture" institutional arrangements, like the committee system in Congress, to exert their influence. They accomplish this by lobbying members to serve on committees that oversee the group's interests, and by lobbying steering committees to assign allied members to these committees.
To support this claim, I develop a method to classify interest groups according to how concentrated their issue interests are within committees in Congress. Using this measure, I predict that groups with concentrated committee interests will be more likely than groups with diffuse interests to get involved in the committee assignment process. Interviews with lobbyists and former members of Congress yield evidence that interest groups influence committee requests, lobby steering committee members, and that concentrated groups are more likely to employ these strategies than groups with diffuse interests. Finally, I use data on committee requests from the 102nd to 110th Congress to provide a quantitative test of my theory. With these data, I find that campaign contributions from groups under each committee's jurisdiction do predict freshman committee requests. That is, contributions from groups under the authority of a given committee are significant predictors of requests to serve on that committee. In sum, this institutional capture theory of interest group influence explains why members request to serve on the committees that they do, and how interest groups are able to influence legislation without pressuring members on roll call votes or otherwise persuading them on particular legislation.