Jonathan links below to Adam Liptak’s front-page New York Times article on the ideology of law clerks, and Jason Mazzone’s critique of it. Echoing the point at the end of Mazzone’s critique, I think the ideology of law clerks roughly matches that of the Justices because the Justices are trying to solve the principal-agent problem. As Wikipedia explains:
In political science and economics, the problem of motivating a party to act on behalf of another is known as ‘the principal–agent problem’. The principal–agent problem arises when a principal compensates an agent for performing certain acts that are useful to the principal and costly to the agent, and where there are elements of the performance that are costly to observe. This is the case to some extent for all contracts that are written in a world of information asymmetry, uncertainty and risk. Here, principals do not know enough about whether (or to what extent) a contract has been satisfied. The solution to this information problem — closely related to the moral hazard problem — is to ensure the provision of appropriate incentives so agents act in the way principals wish.
Supreme Court Justices solve the principal/agent problem by tending to hire law clerks who generally agree with their bosses’ views of the law. That agreement gives the Justices more confidence that their law clerks will be faithful agents without the Justices having to engage in costly monitoring of law clerk performance.
I think this happens roughly equally among the liberal and conservative Justices. The data Liptak presents misses this a bit by suggesting that the trend is more pronounced among the conservative Justices. Justice Thomas has never hired a clerk who worked for a Democratically-nominated circuit judge, Liptak notes. In contrast, Justice Breyer hires clerks who worked for GOP-nominated circuit judges on a regular basis. The numbers are accurate, but in my view, they don’t reflect a greater willingness among liberal Justices to hire conservative clerks than conservative Justices have to hire liberal clerks. Rather, I think the numbers reflect the fact that the pool of today’s circuit court law clerks is considerably to the left of the pool of today’s circuit court judges.
Consider the dynamic. Because the pool of potential circuit clerks is more liberal than the pool of existing circuit court judges, ideological mixes between clerk and judges tend to be one-way. Specifically, it is common for many GOP-nominated circuit court judges to hire liberal clerks. After all, most of the applicants out there are liberal. Even if you slightly prefer conservative candidates, you’re likely to end up with lots of liberal clerks given the pool. In contrast, it is rare for a Democratically-nominated circuit court judge to hire a conservative clerk. (Not unheard of, but rare.) If you’re a Democratically-appointed circuit judge, and you slightly prefer liberal clerk candidates, you’ll find you have tons of qualified liberal applicants to choose from.
This dynamic then leads to the chart we see in the Liptak article with conservative Justices hiring almost exclusively from GOP-nominated circuit court chambers while liberal Justices have a more mixed record. If you’re a conservative Justice, you’ll find ideological matches only in the ranks of alumni of GOP-appointed circuit court judges. On the other hand, if you’re a liberal Justice, you’ll find ideological matches among the alumni of both Democratically-appointed circuit court judges and some GOP-appointed circuit court judges. To put some names on it, a liberal Justice can hire lots of Boudin clerks, and an occasional Kozinski clerk or Wilkinson clerk, without hiring a clerk who is actually conservative.
Finally, I should point out that all of this discussion is of course very much oversimplified. Terms like “liberal” and “conservative” are blunt and often misleading labels. Each Justice, and each clerk, has a wide range of views that often are hard to classify. Still, I think the oversimplification at least leads to some helpful generalizations, even if it’s important not to look at the problem with too simple a lens.