One legacy that Justice Anthony Kennedy leaves as he retires after three decades on the US Supreme Court is some principled guidance on how to hold a dignified debate over choosing his successor. As members of the Senate arm themselves for a battle royal over President Trump’s nomination, they may want to build on, rather than ignore, his judicial legacy. When he wrote the court’s official opinions, Justice Kennedy often sought a path for many of those who lost their legal case to see their views expressed in policy.