Solicitor General Elena Kagan remains high on the list to replace John Paul Stevens, a White House official admitted earlier in the week. An excellent legal résumé and experience arguing before the Supreme Court qualifies her over other candidates, some of whom have too little bench experience, others with too many declared positions. But it’s precisely Kagan’s strength that is also her weakness. Kagan has taken part in dozens of cases (either in oral argument or in briefs) since taking office last January. That means that over the next two to three years, Kagan would have to recuse herself from as many as half of the cases heard by the court—a number extraordinarily higher than normal for freshmen top jurists. The court's majority, then, would shift to 5-3—a tough hurdle to mount, especially for the left wing of the court, which will have lost its most consistent member.
The best example of what Kagan's appointment would look like is her former boss, Thurgood Marshall, for whom she clerked after law school. Marshall had a two-year stint as solicitor general from 1965 to 1967, and when promoted to the court’s bench, recused himself from 98 of 171 cases during his first year. That's 57 percent. Now, the number of cases in which the U.S. takes part is much higher than it was in the 60s. That means Kagan's recusal rate would even greater—approaching, some analysts have said, 70 or even 80 percent. Her participation would gradually increase over time, but sitting on the sidelines for the first few years would make her look fairly ineffectual, especially as Obama heads for reelection and tries to explain to his base what he did for them on the court.
One other drawback of Kagan is, well, her blank slate. Usually a lack of public legal opinions works in a nominee's favor, especially in silencing opponents who would dig up every detail of her past. But for Obama, who presumably wants to shape the court in his vision (empathy is a key quality in a jurist, he has said), Kagan is an ideological wild card. She likely wouldn't tip her hand far in a private interview with Obama, and would certainly stay mum during confirmation hearings. The risk is that she'd become like David Souter, a George H.W. Bush nominee that ended up often ruling against the president who appointed him. Could Kagan end up joining the right-leaning wing of the court? There aren't many ways to know for sure.