On March 20, a man named Keith Clay died in Texas. His death was largely unremarkable except for one thing: he was the 300th person executed in Texas since the U.S. Supreme Court reauthorized capital punishment in 1976. One need not ignore the savagery of his crimes--prosecutors said Clay stood by while a friend murdered a father and his two kids on Christmas Eve 1993, 11 days before Clay himself butchered a store clerk--to pause at his execution.
Three hundred is an impressive milestone, not only because it exceeds the number of executions in the next five top death-penalty states combined,...