If you want to weaken gerrymandering, avert government shutdowns, reduce the concentration of power among politicians, blunt the influence of money in elections, loosen the grip of national media narratives, lower the cost of running for office and give voters a stronger sense that their voice matters, there is a single structural reform for that. If Congress won’t revisit the Reapportionment Act of 1929, then the Supreme Court should. That century-old law’s obsolescence is responsible for many of the country’s most persistent frustrations. It gives rise to districts so large they feel abstract; campaigns so expensive they depend heavily on...