U.S. Supreme Court majority opinions determine law and wield the authority to alter the scope of public policy, but we know very little about how the justices work together to produce legal rules. This paper presents evidence from a novel historical dataset to examine the bargaining process between the majority opinion author and the other members of the Supreme Court. It, in part, seeks to determine whether certain justices—like the famed median seat currently occupied by Justice Kennedy—are more effective at influencing legal policy.