Using the Martin-Quinn ideology scores, we show that U.S. Supreme Court justices strategically respond to Supreme Court membership change. At the aggregate level, the Court moves to counter-balance the ideological change brought about by a new justice. The behavior is most prevalent in 1938-1948, which we call a period of “Constrained Liberalism” and 1975-1995, which we call a period of “Constrained Conservatism.” Counter-balancing is less prevalent throughout the 1950s – early 1970s when justices either ignored or amplified ideological shifts caused by the membership change (especially liberal shifts in 1960s). At the individual level, membership change in the conservative direction leads to a greater response from liberal justices while a change in the liberal direction leads to a greater response from the conservative justices. One implication of our results is that the prevalence of this counter-balancing reaction to membership change has a stabilizing effect on the aggregate ideology of the Supreme Court.

Over the past half-century, students of democratic representation have investigated the extent to which elected officials act as their constituents prefer. Less attention has been paid to the fact that in addition to popular sovereignty, however, modern republican democracy is characterized by the values of liberty and equality. Democratic theorists suggest that these latter values should prevail in cases of conflict when the issue in question speaks to citizens’ fundamental rights, as is the case with gay marriage. We examine this question of representation and responsiveness with respect to gay marriage, an issue of importance to the gay community—a small and intense group that struggles to achieve policy success. We find that neither majoritarian nor capture-based theories of representation fully account for the lack of elected official responsiveness to this particular constituent interest group. Instead, our evidence supports the theory of subconstituency politics. Consequently, we find little reason for optimism that legislation supporting gay marriage is likely to pass both because gay marriage is opposed by a competing subconstituency, Evangelical Christians, who are intense and larger in number and because the systemic design inhibits the ability of minority groups to succeed legislatively in the face of comparable minority opposition.