Does President Obama's selection of Elena Kagan as a Supreme Court nominee mean that we have a potentially strong liberal challenger to the court's increasingly rightward drift? A New York Times analysis points to a fundamental difference in the nominees chosen by Republican and Democratic presidents:
The selection of Solicitor General Elena Kagan to be the nation’s 112th justice extends a quarter-century pattern in which Republican presidents generally install strong conservatives on the Supreme Court while Democratic presidents pick candidates who often disappoint their liberal base.
Ms. Kagan is certainly too liberal for conservatives, who quickly criticized her nomination on Monday as a radical threat. But much like every other Democratic nominee since the 1960s, she does not fit the profile sought by the left, which hungers for a full-throated counterweight to the court’s conservative leader, Justice Antonin Scalia.
Indications are that Kagan will not be that "full-throated counterweight":
Where exactly Ms. Kagan would fall on that scale is unclear since she has never been a judge. She has been a forceful critic of the ban on openly gay men and lesbians serving in the military, but has argued for strong executive power, a hot issue since the Sept. 11 attacks. Some analysts even say Ms. Kagan would actually shift the court somewhat to the right when compared with Justice John Paul Stevens.
...[Conservative leader Leonard A.] Leo said he assumed she would be a reliable liberal but not a Scalia for the left. “Kagan’s probably a vote,” he said, “but probably not the full package."
As Senator Tom Harkin (D-IA) put it, “Why do the conservatives always get the conservatives, but we don’t get to get the liberals? What the hell is that all about?”