Michael Gerson writes:

Kagan has been a leader in the field of law without having a distinctive legal voice. She has been a leader in academia without having left a discernible academic mark. We know little about her views and values — and we are not intended to know much about them. This has become the path of least resistance to the Supreme Court — being eminent without being conspicuous. …

Yet Kagan’s expansive silence leaves a broad range of plausible interpretations. Is she a temperamental moderate who doesn’t like comprehensive pronouncements or judicial activism of any kind? Is she a consensus-oriented liberal who will be able to pull Justice Anthony Kennedy to the left on key votes? Is she is a committed progressive who has carefully hidden her views? Is it possible Kagan lacks any well-formed constitutional perspective at all? Who knows? Who could possibly know?

Conservatives are tempted to scoff — Obama wouldn’t have nominated anyone he had any doubt was a committed judicial activist, right? Let’s be honest: Kagan’s a Democrat and a liberal — we know that from her service in two administrations and her plentiful political donations to Democratic candidates. But the problem with ciphers — as Obama should know all too well — is that they have the ability to convince diametrically opposing combatants that they are “with you.”

So we don’t know how doctrinaire or malleable she is and how much respect she has for precedent. Is she going to be the left’s Sandra Day O’Connor or its Clarence Thomas? For conservatives, it’s nice to think we have a chance to see the other side “waste” a Supreme Court pick for a change. But we shouldn’t bank on it.