While the outsized influence that Big Money is having on federal elections is well-documented, the local impact of the Supreme Court’s 2011 Citizens United ruling has not been fully realized—until now.

The Brennan Center for Justice at New York University School of Law on Sunday published a landmark report (pdf) documenting how secret donations have corroded democracy at the state level, where it is “arguably most damaging.”

“Mining companies secretly targeting a legislator who opposed permits. Food companies battling a ballot measure to add labeling requirements. Payday lenders supporting an attorney general who promised to shield them from regulation,” writes Brennan Center president Michael Waldman, listing the ways that outside money has corrupted local politics.

According to the report, secret spending on the local level rose from 24 percent in 2006 to 71 percent in 2014. This is largely due to a new phenomenon the authors have dubbed “Gray Money,” which is when “organizations, which are legally required to disclose their donors, route money through multiple layers of PACs to obscure its origin.”

The first of its kind survey analyzed spender and contributor reports in six geographically and demographically diverse states, where sufficient data was available: Alaska, Arizona, California, Colorado, Maine, and Massachusetts. The sample represents approximately 20 percent of the nation’s population. 

The lower cost of state and local elections makes it relatively easy for dark money to dominate. According to the study, outside groups often outspent candidates by the $10,000’s to lower $100,000’s, which it notes is “a modest business expense for special interests, but a major hurdle for many candidates and community groups.”