Are Supreme Court justices with prior experience in the executive branch more likely to defer to the president in separation of powers cases? While previous research has suggested that such background may signal judicial policy preferences but does not shape them, I argue here that institutional socialization may indeed increase future judicial deference to the president. Using an original data set of executive power cases decided between 1942 and 2007, I model justice-votes to test this hypothesis. I uncover three noteworthy findings: (1) a clear correlation between prior executive branch experience and support for the executive branch, (2) the degree of this support intensifies as executive branch tenure increases, a finding congruent with a socialization hypothesis, and (3) contrary to received wisdom, executive powers cases possess a clear ideological dimension, in line with the expectations of the attitudinal model.
In 2005, on the well-respected legal blog Opinio Juris, law professor Julian Ku reflected on the likelihood that then Judge Roberts would be a strong supporter of executive power once on the Supreme Court. After noting that Roberts had clerked for former Chief Justice Rehnquist, also a supporter of a robust executive branch, Ku stated that "like Jackson, who served as Attorney- General for FDR, and Rehnquist, who served as an Assistant Attorney General for Nixon, Roberts' main government experience has been in the executive branch as associate White House Counsel and Deputy Solicitor General" (Ku 2005). The implication of this statement was clear: as a former member of the executive branch, Judge Roberts was expected to be more deferential to the president in cases involving executive power.
The notion that background affects behavior might seem an obvious truth. When it comes to judicial decision-making, however, particularly for hard cases at the appellate court level, the study of social and background characteristics as systematic correlates for behavior has attenuated, thought to have fallen short on both theoretical (Sisk, Heise, and Morriss 1998) and empirical grounds (Heise 2002). The successor to the social background model has undoubtedly been the attitudinal model, which posits that such cases are mainly resolved according to the ideological policy preferences of the judges who hear them (Segal and Spaeth 1993). However, though ideological attitudes are the single best extralegal predictor of judicial decision-making, a great deal of variance remains unexplained. Moving to fill this gap, legal scholars have provided persuasive arguments as to the role that legal doctrine (Bailey and Maltzman 2008; Richards and Kritzer 2002), strategic interaction (Epstein and Knight 1998), the desire for comity (Hettinger, Lindquist, and Martinek 2007), and even the need for approval (Baum 2006) play in explaining judicial decision-making when the law is unclear.
While not returning to their place of prominence, social background models remain useful, primarily in improving predictions of judicial decision-making where a reasonable connection can be drawn between the case area and the background in question. These studies have not only used better methods and reduced incomparability to uncover noteworthy correlations between social background factors and decision outcomes (Brudney, Schiavoni, and Merritt 1999; Schneider 2002; Sisk, Heise, and Morriss 1998), but have even successfully tested competing causal explanations (Boyd, Epstein, and Martin 2010).
In this study, I follow this more recent vein of social background studies, contending that executive branch experience has predictive power in explaining separation of powers outcomes on the Supreme Court. Specifically, I build on work by Michael Dorf, who found that in the post-Warren Court era, Republican Supreme Court appointees with executive branch experience were more likely to be consistent conservatives than those who lacked such experience (Dorf 2007). …