Randy's lessons below are interesting ones, but I'm not so sure I agree with him. In any confirmation process, the Senators try to get a sense of what a nominee is likely to do if the Senate agrees to give that person the tremendous power of the office to which he or she has been nominated. Constitutional theory is clearly relevant, but it's only part of the picture. Few judges are constitutional theorists, and those that try to be usually aren't very consistent or very good at it. Given that, I can see why the nominations debate would go beyond questions of constitutional method.