So, Elena Kagan is now our nominee for the Supreme Court. I will go into more detail about this later, but there shouldn't be any sugarcoating -- it's a poor choice.
One way of seeing this is to examine Marty Peretz's attempted defense. Boil off the usual ad hominems and you're left with no actual real credentials for the position attributed to Kagan. He doesn't try to argue that Kagan -- who has no judicial experience, very limited political experience, and no record of influential scholarship -- is a better choice than Diane Wood or Sidney Thomas, because the proposition is pretty much indefensible. When you're reduced to noting that a prospective nominee for the highest court in the land is a "brilliant conversationalist" and that other Harvardites think she's good people, one has pretty much conceded that the pick is Ivy League nepotism of the worst sort. The idea that the complete absence of evidence about her constitutional vision is no big deal is something that's easy for someone who will never be denied an abortion, be discriminated against by an employer, etc., to say, but for people who actually take such things seriously it's rather important.
As the conservative reaction to Harriet Miers indicates, conservatives do take their constitutional values seriously. I suspect we're about to find out that far too many liberals don't. And if a more Republican future Senate rejects or filibusters Obama's next nominee down the road, this will rank as a blunder on a par with Reagan's failure to nominate Robert Bork while the GOP still controlled the Senate. You don't waste a pick on a blank-slate centrist when your position in the Senate is about to get dramatically weaker.