Before the 2010 Supreme Court decision known as Citizens United, all money spent in federal elections urging the election or defeat of a candidate had to originate from identifiable human beings. Corporations and unions were forbidden from involvement beyond organizing individuals' contributions. Then Citizens United struck down the prohibition ... so corporations had the right to spend unlimited money espousing their political views. This was the birth of Super PACs. Citizens United [also] opened ... paths for foreign money to flow into the U.S. political process. The 2016 election has seen a surge of contributions to Super PACs by so-called ghost corporations, which appear to exist solely to make those donations and whose ownership is unknown. Almost all large publicly traded U.S. companies have some degree of foreign ownership. Any donations by such corporations are technically partially of foreign origin. Nonprofit corporations ... have always been able to accept unlimited donations from individuals or corporations, but before Citizens United, could engage in little federal political activity. Now, thanks to the combination of Citizens United and a 2007 Supreme Court decision, "social welfare" organizations ... and trade associations [can] make independent political expenditures just like Super PACs. Unlike Super PACs, they are not required to publicly disclose their donors. This is why contributions to politically active nonprofits are often referred to as "dark money."