Dale Carpenter is not amused by this line of inquiry.
One can fully accept that political allegiances and the Supreme Court’s own desire to preserve the perception of its legitimacy, which is itself a form of politics, can influence its decisions. But Feldman’s approach calls on us to examine the deep and hidden psychological motivations of the Justices–which he agrees they would deny publicly and privately–without even considering whether there are perfectly reasonable and defensible legal grounds for the way they may rule in a particular case.I am sympathetic to Carpenter's concerns. But I think some of them may be, if not dispelled, at least allayed if we look into the psychological literature which seems to underlie Feldman's argument (Feldman does not cite this literature, which probably doesn't help matters).
The phenomenon Feldman describes, to my eyes, seems most similar to the idea of "moral credentialing." I discuss this concept a bit in Sticky Slopes, but the basic idea is pretty simple: People have a strong self-conception of themselves as fair-minded and egalitarian; values which genuinely matter to them. But they also are motivated, often subconsciously, to act in unequal and unfair manners (e.g., racial or sexual favoritism). The first element often acts to check the second; when evaluating job applicants, for example, favoring a man over a woman would threaten the egalitarian self-concept. However, if a person has had the opportunity to demonstrate their egalitarian bona fides, that act provides a "credit" which allows them to engage in discrimination without threatening their self-image. Call it the "how can I be racist, I donate to inner-city charities!" effect. Having a salient egalitarian act one can point to makes it harder for observers (or the self) to infer that one makes biased decisions; paradoxically, this makes people more likely to indulge in precisely that sort of bias.
One can easily apply this same logic to judges, who have private "political" motivations regarding case outcomes that exist alongside a genuine commitment to fair and neutral arbitration that rejects the validity of relying on such preferences. For this reason, judges are undoubtedly quite sensitive when their legal rulings "just happen" to match their policy preferences -- it raises the specter that their decisions are actually motivated by politics rather than law. An easy way to dispel those fears is to point to another case which doesn't fit that mold. "If I were the sort of judge who voted on political grounds, how do you explain my vote in X v. Y?" Having this credit, the judge can effectively discount the possibility that he or she is influenced by such political concerns -- and accordingly will be less like to check against the subtle impact such desires have on his or her reasoning. I'll admit to having a similar suspicion regarding the latest health care case, albeit linked not to a gay marriage ruling but to Chief Justice Roberts' vote in the original Obamacare decision. That vote provides the Chief with a "credit" demonstrating that his votes on this subject are law-based rather than motivated by any antipathy to the Affordable Care Act or Obama administration. Consequently, it would be much harder to assert that a subsequent vote against the federal subsidies is motivated by bias -- after all; if he was the sort of judge that would be swayed by such concerns, why wouldn't he have simply struck down the law tout court?
Returning to Carpenter's objections, he complains that Feldman does not account for entirely legitimate, law-based reasons one might vote "conservative" in the health care case and "liberal" in the gay marriage cases. But moral credentialing, like all forms of motivated cognition, operates in the space of ambiguity -- it wouldn't work unless there were credible neutral reasons supporting one's (politically) preferred outcome. No moral credit of racial egalitarianism will enable one to justify hiring a drunk White high school dropout over a Black valedictorian. Rather, moral credentialing comes into play when there are facially legitimate reasons for a variety of different actions: a job opening sought by both a qualified White and Black candidate, for instance, where one could legitimately make a case for either. And so it is with law: whatever credit one receives for crossing "party lines" on a high-profile case -- demonstrating one's neutrality as a judge -- can conceptually only be redeemed in a case where reasonable minds might differ.
It is for this reason that Carpenter is partially correct regarding another one of his arguments -- that the psychological motivation forwarded here is "non-falsifiable." He's right, at least at the level of explaining individual cases. If the male and female candidates for a job are both equally qualified -- if there is a solid, credible case for either party -- non-prejudiced decisionmakers should still hire the man roughly half of the time. Any individual decision to hire a man may be entirely neutral and unaffected by the existence of a prior "credit." Where the effects of moral credentialing start to emerge is when we aggregate cases and see that the percentage of women hired plummets amongst actors who have in their possession a salient anti-sexism credential.
And this hypothesis probably could be put to the test with respect to judicial behavior. Are judges who break with their "side" in a high-profile case more likely to indulge in seemingly partisan or political voting in the aftermath? It seems that, measured across a large number of judicial decisions, this is a hypothesis that could be confirmed or falsified. Someone should get on that.