Matea Gold reports today on the first ever randomized field experiment to assess the influence of campaign contributions on legislators’ behavior. While the results shouldn’t come as a surprise to anyone familiar with U.S. politics (spoiler alert: money = access), the study takes a first crack at quantifying exactly how money influences the legislative process.

The authors partnered with CREDO Action, a liberal advocacy group, during a real-world lobbying effort last summer. The group sent out emails seeking meetings with 191 members of Congress, all from the same political party (given CREDO’s political alignment, Gold says it’s safe to assume they were Democrats).

The emails were randomly assigned one of two nearly-identical templates, the only difference being that one template referred to prospective meeting attendees as “local constituents,” while the other referred to them as “local campaign donors.” CREDO and the study authors then tracked whether they were able to obtain meetings with the members of Congress, their senior staffers, or other staffers.

Set up like this, the study sought to answer the following question: Are Congressmen and their senior staffers more likely to grant face-time to potential campaign donors than to other constituents? The results are laid out in the chart below. The authors write:

Senior policymakers attended the meetings considerably more frequently when Congressional offices were informed that the meeting attendees were donors. Only 2.4% of offices arranged meetings with a Member of Congress or Chief of Staff when they believed the attendees were merely constituents, but 12.5% did so when the attendees were revealed to be donors. Members of Congress and Chiefs of Staff were thus five times as likely to make themselves available for putative donors as for constituents.

Two additional points are worth noting: success rates for meetings with Congressmen were low overall, but the study authors note that non-donors rarely obtained any meetings with Congressmen or chiefs of staff. This suggests that being a donor is a near-necessary condition for obtaining high-level Congressional access, but it is not a sufficient one.

Moreover, the study findings directly undermine the logic behind numerous Supreme Court decisions on campaign finance, including Citizens United. In that case, the Court reasoned that because corporate election spending cannot be given directly to legislators, it would not facilitate influence with them. But the study authors note that the donor emails “did not state that the attendees had given to the legislator considering the request, merely that the attendees were ‘campaign donors’ in general. The results therefore support reformers’ assertions that campaign contributions may facilitate influence with a legislator even if not given to that particular legislator.”

In other words, simply alluding to the prospect of a donation was enough get legislators’ attention.