When Louis XVI presented Benjamin Franklin with a snuff box encrusted with diamonds and inset with the King's portrait, the gift troubled Americans: it threatened to "corrupt" Franklin by clouding his judgment or altering his attitude toward the French in subtle psychological ways. This broad understanding of political corruption--rooted in ideals of civic virtue--was a driving force at the Constitutional Convention.

For two centuries the framers' ideas about corruption flourished in the courts, even in the absence of clear rules governing voters, civil officers, and elected officials. Should a law that was passed by a state legislature be overturned because half of its members were bribed? What kinds of lobbying activity were corrupt, and what kinds were legal? When does an implicit promise count as bribery? In the 1970s the U.S. Supreme Court began to narrow the definition of corruption, and the meaning has since changed dramatically. No case makes that clearer than Citizens United .

In 2010, one of the most consequential Court decisions in American political history gave wealthy corporations the right to spend unlimited money to influence elections. Justice Anthony Kennedy's majority opinion treated corruption as nothing more than explicit bribery, a narrow conception later echoed by Chief Justice Roberts in deciding McCutcheon v. FEC in 2014. With unlimited spending transforming American politics for the worse, warns Zephyr Teachout, Citizens United and McCutcheon were not just bad law but bad history. If the American experiment in self-government is to have a future, then we must revive the traditional meaning of corruption and embrace an old ideal.