More than a century ago, President Teddy Roosevelt charged up Capitol Hill to convince Congress to ban direct corporate contributions to federal election campaigns. The Rough Rider, unsurprisingly, got his way. Forty years later, Congress included unions in the ban and extended the prohibition to corporate and union expenditures.

In September, that legacy of campaign finance reform will be in the cross hairs of the U.S. Supreme Court because of a quirky challenge that now has the potential to be an election law blockbuster.