Bernstein acknowledges that we don't know how far to the left she is:
Scott Lemieux notes that what we know now is what we knew going in, that Kagan is "liberal in a broad sense" but that where she sits on the a spectrum "from Larry Summers to Thurgood Marshall...is likely to remain a mystery." He's right -- but I don't think that's a problem with the process. We don't know, because as she approaches a twenty year career on the Court, give or take twenty years, even Elena Kagan probably doesn't know. She's going to evolve and change as she adapts to her new role. And how that happens will be in part her general approach now, in part her specific ideas now, in part unknowable changes in her over time, and in part unknowable reactions between her, the specific cases that the Court will deal with, and her colleagues over time. If we had a nominee with, say, a record of speeches and law review articles stating clear positions on many of the things on which Kagan has no record, the unknowns would still swamp the knowns.