What should President Trump look for in a Supreme Court nominee? Exactly what he did with his selection of Justice Neil Gorsuch and his slate of lower-court nominees. He should ask one question: Who is best at being a judge, as demonstrated by a consistent record of applying textualist and originalist reasoning to significant legal questions? Given the reported options Mr. Trump is now considering, the answer is obvious: Judge Brett Kavanaugh of the U.S. Court of Appeals for the District of Columbia Circuit.

I’ve known Judge...