In every case in which the United States Supreme Court hears oral argument and decides by an opinion or judgment of the Court, the justices vote twice: once in secret conference and again when they hand down the final decision. We examine two main aspects of the relationship between fluidity (i.e., vote-switching between the two votes) and coalition sizes: (1) the relationship between switching and the size of the coalition at the conference vote, and (2) the relationship between switching and the size of the coalition at the final vote. Unlike previous studies, we examine all types of switching that can occur between the conference and final votes.

Our results highlight two effects: (1) majority effects (i.e., the tendency of members of a majority coalition at the conference vote not to switch, and the tendency of the fluidity to increase the size of the majority coalition); and (2) unanimous effects (i.e., the tendency of members of a unanimous coalition at the conference vote not to switch and the tendency of die fluidity to generate a unanimous final vote). Unanimous effects have not been previously identified in the literature.