The Wisconsin Club for Growth filed as a tax-exempt 501(c)(4) “social welfare” organization in 2011 and 2012, telling the IRS that it spent “$0” for political purposes. Unlike political campaign committees, such groups can accept unlimited donations and do not have to disclose their donors. According to IRS rules, they are allowed to engage in political activity so long as it’s not their primary focus.

“Given the intricate, elaborate, and time-consuming work that Wisconsin Club for Growth was doing in 2011 and 2012 to run this secret and coordinated fundraising, strategizing and advertising campaign, it is abundantly clear from the emails released in The Guardian story that engaging in political campaign activity was the primary activity of Wisconsin Club for Growth, in violation of the IRS regulations,” the WDC complaint states.

In 2014, the liberal Center for Media and Democracy filed a complaint with the IRS leveling similar allegations. That complaint came after court documents from the John Doe case were briefly posted on a federal court website, revealing the investigation found Walker campaign advisers discussing how to use the Club as a hub for raising millions of dollars in undisclosed contributions and disbursing it to dozens of conservative political groups. The status of that complaint is unknown as the IRS does not comment on investigations.