Politically active so-called "dark money" groups spent more than $50.7 million on direct advocacy at the height of the midterm campaigns last year, but just 8 percent of that money came from groups that identified some of their donors, according to a new analysis by the Campaign Legal Center.

The finding comes despite a recent court decision that seemed to open a path to increased transparency. The August decision from the U.S. District Court for the District of Columbia in Citizens for Responsibility and Ethics in Washington v. the Federal Election Commission required all groups making independent expenditures – spending on things like advertisements or mailings that directly advocate for or against a candidate – to report the names of donors that contributed money for political purposes.

But the center's report, issued Wednesday, concludes that just a few months removed from that decision, most of these organizations have sidestepped the new rules. It draws on year-end reports from the 2018 midterms that show most dark money operations – which include nonprofits and other corporations – are remaining dark, indicating to the FEC that they did not receive any donations expressly for political activities.

Majority Forward, a nonprofit corporation that spent more than $40 million on independent expenditures supporting Democratic candidates in the 2018 cycle, disclosed none of its donors, noting that "as a matter of policy, Majority Forward does not accept funds earmarked for independent expenditure activity or for other political purposes in support or opposition to federal candidates."

That seems unlikely, according to the Campaign Legal Center.

"It strains credulity for groups like Majority Forward, Patriot Majority USA, and Texas Organizing Project to claim that no donors gave for political purposes," the group says in its report, naming other prominent dark money operations that also did not disclose their donors. "These groups may be calculating that the FEC is unlikely to second-guess these implausible assertions."