To understand today's Supreme Court, it is essential to understand the judicial philosophy of its swing vote. For twenty years, Justice Anthony M. Kennedy has voted with the majority more than any of his colleagues. He has provided the deciding vote in cases involving politically charged issues such as affirmative action, the 2000 presidential election, religious expression, gay rights, and executive power to detain suspected terrorists. With a record reliably neither liberal nor conservative, Kennedy has generally been viewed as a capricious, indecisive moderate.

Frank Colucci, however,...