Curbing is effective when the court and congress are ideologically divergent.

The most obvious and understandable explanation for the proposition of Court-curbing legislation is that members of Congress are more likely to propose such legislation as their own ideology diverges from that of the Court.1 Members of Congress will inherently attempt to pursue their own ideological interest and oppose those interests which run counter to them (Meernik and Ignagni, 1995). Therefore, members of Congress are more likely to attempt to curb the Supreme Court when the Court is ideologically opposed to them. This does not mean that a member of Congress will necessarily react to individual Court decisions that involve opposing ideological rhetoric – although they very well may, but that is a different research question; rather, it means that members of Congress are more likely to contest and curb a Court that they perceive as ideologically opposed in general (Henschen, 1982). In other words, no action on the part of the Court is necessary to bring about Court-curbing proposals; if the Court as a whole simply possesses ideological opinions that are divergent from a particular member of Congress it is more likely that that member of Congress will propose Court-curbing legislation.

This relationship is the result of fairly typical and common political behavior. When two institutions – or even individuals – are ideologically opposed and routinely in competition over policy preferences, it is likely that they will seek to curb the other and bolster their own policysetting capacity. This behavior is a straightforward attempt at achieving a greater likelihood of obtaining policy preferences in the future, by way of weakening a rival in the present.

Members of Congress will seek to curb an ideologically divergent Court more frequently than they would an ideologically allied Court. However, it is not the case that ideological alignment is sufficient to prevent all efforts of individual level court-curbing, although it is arguably necessary. It is also the case that ideological divergence is not the same as party divergence. The Supreme Court is not dominated – or even substantially affected – by party politics or “party lines” and is therefore not likely to draw the wrath of Congresspersons simply as a result of party differences (Howard and Segal, 2004; Bartels, 2011). Ideology, on the other hand, has a clear and powerful effect over how the Supreme Court chooses and decides cases, thus making it a point of interest and worry for members of Congress (Howard and Segal, 2004; Lindquist and Solberg, 2007).