Bargaining Power in the Supreme Court: Evidence from Opinion Assignment and Vote Switching

How can we assess relative bargaining power within the Supreme Court? Justices cast two votes in every case, one during the initial conference and one on the final merits of the case. Between these two votes, a justice is assigned to draft the majority opinion. We argue that vote switching can be used to detect the power of opinion authors over opinion content. Bargaining models make different predictions for opinion content and therefore for when other justices in the initial majority should be more or less likely to defect from initial positions. We derive hypotheses for how opinion authorship should affect vote switching and find that authorship has striking effects on switching. Authors thus have disproportionate influence and by extension so do Chief Justices, who make most assignments. This evidence is compatible with only the “Author Influence” class of bargaining models, with particular support for one model within this class. This contains vote switch data and coalition level data.