No one is surprised that Elena Kagan is President Obama's pick to replace Justice John Paul Stevens. Like Sonia Sotomayor last year, she is someone sure to be confirmed by the Senate and will require little of the president's political capital. Kagan is impeccably qualified. Unlike other recent nominees, she has a small paper trail. She's never been a judge, so there are no prior opinions to scrutinize. She's written only five major law review articles, and none are controversial.

On the other hand, that is the risk in Obama's selection of Kagan: no one is sure of her views on key issues. Presidents who have picked nominees without a paper trail often have been stunned by the results. David Souter, for example, had been a justice on the New Hampshire Supreme Court, but no one knew where he was on the ideological continuum. He deeply disappointed Republicans after being selected by President George H. W. Bush when he turned out to be a fairly liberal justice. No one knows whether Kagan will be as liberal as Stevens, more conservative or even more liberal. And no one will know until she's on the high court.