Many have speculated that President Obama could have the power to shape a new Supreme Court. Some predict he could have as many as three Supreme Court appointments in his first term alone, given the ages and political persuasions of the current Justices.
Commentators tend to believe that turnover is most likely to occur at the liberal end of the Court, which includes Stevens (88), Ginsburg (75), Breyer (70), and Souter (69). Although Souter is the youngest of the four liberal Justices, he has reportedly expressed interest in returning to his home in New Hampshire, triggering speculation that he might retire. It is considered less likely Obama will get to fill a vacancy left by one of the conservative members of the Court, which includes Scalia (72), Kennedy (72), Thomas (60), Alito (58), and Roberts (54).
Given this landscape, it is not entirely clear how Obama can shape the Supreme Court with potential nominees. Some have argued that he won’t be able to change the Court at all if he’s merely able to replace one liberal Justice with another, while others have argued that replacing moderately liberal Justices with more full-throated liberals could have a significant impact on the Court. At the bottom of this disagreement lies a question of how Supreme Court case outcomes are determined.
Last Wednesday Professor Tonja Jacobi presented a paper to the Workshop on Judicial Behavior that attempted to answer that question. Jacobi and her coauthor, Professor Matthew Sag, attempted to empirically test what determines Supreme Court case outcomes, focusing on three potential models of judicial behavior: the Ideological model, the Collegiate model, and the Strategic model.
The Ideological model of judicial behavior is based on the attitudinal model of judicial decisionmaking (previously discussed here). Essentially, it is a minimum winning coalition model because it is premised on the idea that judges only care about case outcomes and are not willing to further compromise to attain additional votes once they have secured a five-Justice majority. Therefore, according to the Ideological model, “every case should reflect the preference of the median of the Court.” As a result, the Ideological model suggests that the Court should not significantly vary from case to case (assuming the composition of the court and the ideologies of the Justices remain stable) because the outcome will always be determined by the ideology of the median Justice, which varies little.
According to the Martin-Quinn scores, which measure judicial ideology based on the actual votes of Justices, in 2006 the ideological landscape of the Court looked like this:
Assuming the Justice’s ideologies have remained relatively stable since 2006, the Ideological model predicts that case outcomes will always mirror the ideological position of Justice Kennedy. Therefore, according to the Ideological model, Obama could not substantively change the outcome of Supreme Court cases if he were to fill vacancies left by Stevens, Ginsburg, Breyer or Souter, assuming none of his appointees were more conservative than Kennedy. If, on the other hand, Obama were able to nominate a replacement for Kennedy or any of the conservative Justices, he could greatly alter Supreme Court jurisprudence because he’d have the power to make Justice Souter the new median vote.
Under the Ideological model, replacing any of the conservative Justices with a Justice to the left of Kennedy would move the court to the left. But interestingly, the impact of a potential Obama appointee on case outcomes would be identical if Obama were filling a vacancy left by the most conservative member of the Court (Thomas) or the current median Justice (Kennedy). Similarly, under the Ideological model, it wouldn’t matter whether Obama were filling a vacancy left by the most liberal Justice (Stevens) or the most moderate liberal (Souter), because Kennedy would continue to be the median Justice. And, because the Ideological model focuses on the median Justice (rather than a mean of the Justices' ideological scores) Obama could fill a vacancy left by a liberal Justice with a radical liberal or with someone just barely more liberal than Kennedy (or even with the exact same ideological views as Kennedy) and there would be no impact on case outcomes because the median Justice would remain stable (of course these choices would matter over time as additional Justices retired).
The Collegiate model, by contrast, is a maximum winning coalition model because it is grounded on the belief that Justices care deeply about building coalitions. Under this model, Justices will be willing to compromise their positions to whatever extent is necessary – short of reversing the Court’s ruling – to persuade an additional Justice to join the majority (even after a five-Justice majority has been attained). Under the Collegiate model, the outcome of a case mirrors the ideology of the “last Justice in.” The last Justice in will always be either the most liberal member of a conservative majority or the most conservative member of a liberal majority. Under the Collegiate model, cases “should reflect the most extreme Justices within the coalition, that is, the Justice whose preferences are closest to the dissenting Justices” because in order to attain the vote of the last Justice in, the majority has to shift its opinion to accord with that Justice’s preferences.
Let’s again look to the Martin-Quinn landscape:
The effect of potential Obama appointees is fuzzier under the Collegiate model. Although Kennedy’s ideological position would still be determinative in all 5-4 opinions, under the Collegiate model we’d expect to see fewer 5-4 decisions, because Justices care about building coalitions and are willing to compromise their ideal positions to garner additional votes.
An important point discussed at the Workshop is that it does not matter why the Justices want to build larger coalitions. It may be because they want to get along with their colleagues, but it may also be because they care about establishing strong precedents and therefore prefer a strong precedent that is a bit to the left or right of their ideal point to a weaker precedent that perfectly conforms with their ideology.
Under the Collegiate model it is less clear that turnover on the liberal end of the court couldn’t change case outcomes. In all 5-4 decisions, Kennedy would be the “last Justice in” and so his ideological position would determine the court outcome. But in decisions branded as “conservative” (pro-IP rights, for example) 6-3, 7-2, 8-1, or 9-0 decisions would be determined by the most liberal Justice in a conservative majority.
What is interesting about the Collegiate model is it appears that Obama could have the greatest impact on Supreme Court case outcomes by replacing one of the current liberals with a more moderate liberal, just to the left of Kennedy. This is because an even more moderate liberal would be most likely to be the “last Justice in” in a conservative majority. This would mean that Obama’s appointee could consistently move the outcome of conservative Supreme Court cases to the left, up until the point at which that moderate liberal would join the dissent. At the same time, this moderate appointee would have no impact on liberal Supreme Court decisions, because Kennedy, would continue to be the least conservative “last Justice in” possible for liberal opinions.
Finally, the Strategic model suggests that cases will reflect the mean ideological scores of the majority coalition. This is because, under this model, every case represents a compromise between the Justices in the majority.
Let’s take one more look at the Martin-Quinn continuum:
Because the Strategic model focuses on the mean ideological position of the Justices in the majority coalition, it suggests that Justices with extreme ideological positions have a significant impact on case outcomes. As a result, if Obama appointed a Justice more liberal than Stevens to the court it would have the effect of consistently moving liberal decisions further left. By contrast, appointing a Justice just to the left of Kennedy would have very little impact on conservative case outcomes because the mean of the conservative majority Justices would change very little. This shows that the Collegiate and Strategic models of judicial behavior predict that the ideology of Obama’s potential appointees will have radically different effects on case outcomes.
It is notable that the skewing effect of outliers discussed above is somewhat lessened because Justices can concur. Consider, for example, Thomas’ view of the Commerce Clause that led to his concurring opinion in United States v Lopez.
In addition to these three models, Jacobi also tested an additional variation of the Strategic model that focuses on the ideological score of the median Justice in the majority, rather than the mean of the majority Justices’ ideological scores, to predict case outcomes.
Under this variation of the Strategic model, ideological outliers matter less and so a radical appointment would have little impact. To illustrate the differences between the two variations of the Strategic model, imagine that Stevens retires. Under the “mean” version of the Strategic model, appointing a Justice to the left of Stevens will move liberal case outcomes further left because that new Justice’s ideology is averaged with the ideological scores of the rest of the majority. By contrast, under the “median” version of the Strategic model, replacing Stevens with a more liberal Justice would have little impact, because the median Justice in a liberal majority would be unaffected.
The complicated tools Jacobi used to test these models (outlined in great detail in her paper, available here) are beyond the scope of this blog post, but the results she reached should be of interest to our new President: the Strategic model emerged as the most reliable predictor of case outcomes. This was true regardless of whether the mean or median of the majority was used, but Jacobi indicated that she found the mean variation of the Strategic model preferable.
If Jacobi is correct, then the mean ideological score of the majority coalition determines case outcomes. This is interesting, because it would mean appointing a Justice more liberal than Obama’s own ideology (ignoring the fact that confirmation hearings might quash such a nomination) might be a smart move: the ideological position of that Justice would never determine the case outcome, but that Justice would have the effect of moving liberal decisions incrementally to the left. On the other hand, appointing a more moderate liberal (just to the left of Kennedy) to replace someone like Stevens would move liberal decisions significantly to the right but wouldn’t have a significant impact on conservative case outcomes.
Of course, the above analysis considers the effect of only one Obama appointee. With five of the nine Justices over the age of 70, Obama just may have the opportunity significantly shape Supreme Court jurisprudence.