How secret donations influence US elections

The two most common vehicles for dark money are politically active nonprofits and corporate entities, such as limited liability companies. Certain politically active nonprofits — notably those formed under sections 501(c)(4) and 501(c)(6) of the tax code — are generally not required to publicly disclose their donors. And limited liability companies formed in states such as Delaware and Wyoming are essentially black boxes through which donors can make secret donations to super PACs or to intervene directly in election campaigns...
http://america.aljazeera.com/articles/2016/1/20/how-secret-donations-influence-us-elections.html