My colleauge Paul Wahlbeck, who has written extensively on the Supreme Court and especially the strategic interactions among justices, send along this:
bq. Judicial scholars for decades have studied the justices’ influence. Based on findings in recent research with Jim Spriggs, I conclude that Elena Kagan may wield influence, but it will take time and shifts in the Court’s ideological composition before that is realized.
bq. Looking at private correspondence sent between justices (memos and draft opinions are normally sent to every justice) and correspondence that expresses concerns with an opinion (data available here), we tested two explanations of influence on the Burger Court. Influence could accrue through the agenda-setting powers of leaders (i.e., the chief justice or the senior associate justice) or through ideological placement (i.e., the median justice) (see this paper).
bq. We used network analysis of the Burger Court justices’ interactions to gauge their influence. Consistent with network theory, we assumed that justices with more ties to other justices have greater influence. We found a divergence between the types of interaction. In private communications, including coordination of positions among coalition members, justices holding leadership positions prove to be more influential. In contrast, interactions responding to an opinion’s content reveal that influence is derived from proximity to the median justice. For example, in 1979, the “swing justice,” Lewis Powell, and the senior associate justice, William Brennan, generated more interactions than others.
bq. In either case, if President Obama’s selection of Kagan was aimed at influencing Justice Kennedy to join the more liberal justices, he will be frustrated.
The take-away: influential justices hold leadership positions or are “swing voters.” Kagan will be neither.