The early consensus on Supreme Court nominee Merrick Garland is in, and it's that Garland is a moderate: A former prosecutor, careful in his jurisprudence, and beloved by conservative Utah Senator Orrin Hatch. At best, he's a safe pick. At worst, he's a tragically missed opportunity to appoint a woman, a person of color, or a defense attorney who might bring a different point of view.
Or not. According to one measure of Supreme Court justices' ideology, Garland is hardly less left-wing than Obama's past nominees, Elena Kagan and Sonia Sotomayor.
When political science diverges so strongly from public perception, one of the two is probably wrong. And measuring justices' ideology is a highly imprecise art. Another method places Garland near the center of the court, to the left of Anthony Kennedy but to the right of the existing liberal justices.
This isn't just an academic disagreement. Whether the public perceives Garland to be a left-wing firebrand or a stolid moderate matters in the political fight over filling Antonin Scalia's seat. If Garland is simply a white male Sonia Sotomayor, Senate Republicans can argue Obama isn't even trying to compromise. If Garland is a slightly more left-wing Anthony Kennedy, on the other hand, liberal Democrats can argue that Obama's pick is an utter betrayal.
The measurement that called Garland a liberal wasn't looking at his jurisprudence
There's no foolproof method to precisely measure the political leanings of federal judges. And so political scientists use rough proxies, such as the ideology of the presidents and senators who appoint and confirm judges.
That's the method used by the Judicial Common Score, which says Garland is slightly more liberal than Kagan and Justice Stephen Breyer. Using that metric, he'd become the third most liberal Supreme Court justice:
Obama's potential nominees to replace #Scalia are roughly as liberal as Kagan and Breyer. pic.twitter.com/oGZeTOJJ7n— Mike Salamone (@enomalas) February 16, 2016
But there's a big caveat here. This score isn't based on anything about Garland. It's measuring the ideological leanings of President Bill Clinton, who nominated Garland to the DC Circuit Court in 1995.
The Judicial Common Score, derived by four political scientists, relies on a quirk of Senate procedure. When the Senate Judiciary Committee is considering a nominee, the committee gives the senators who represent the would-be justice a chance to effectively veto the pick.
The Judicial Common Score assumes that the judge's ideology is roughly similar to the senator who represented them when they were nominated, provided the senator and the president are from the same party, because the senator didn't veto them when given a chance.
But Merrick Garland, when he was confirmed to the DC Circuit, lived in Washington, DC. He didn't have a senator to approve or veto his nomination. And so the common score relies on the next best thing: Bill Clinton.
So what it's actually saying is that Garland is no more or less liberal than other Clinton appointees — or if Bill Clinton were appointed to the Supreme Court, he would land somewhere between Sotomayor and Kagan on the left-right spectrum.
But Obama is not appointing Clinton to the Supreme Court. And while Jeffrey Segal, a political scientist at Stony Brook University who helped develop the measure, calls it "a reasonably good predictor" of Garland's future votes, it's clearly far from exact.
Do Garland's moderate law clerks mean he's a moderate?
Another way of measuring Garland's ideology puts him much closer to the center, to the right of Breyer and Kagan but still far to the left of Kennedy:
If confirmed, Garland would be the new median justice. (Based on ideology of judges clerks https://t.co/2TGLwqo6SK) pic.twitter.com/Be6ZrE7FpC— Adam Chilton (@adamschilton) March 16, 2016
This lines up much better with the public perception of Garland. But this isn't based on Garland's record or previous votes, either. It's based on the political leanings of the law clerks he hired to work with him.
The method, published in a working paper on February 29, relies on databases of political donations to determine whether law clerks are liberal or conservative. Then it assumes that the judges who hire those clerks have roughly the same beliefs.
Garland falls in the middle, meaning that either he hired an ideologically heterodox group of clerks — some Republican donors, some Democratic donors — or that his clerks themselves donated in a way that suggests they're political moderates.
"He’s definitely to the right of Breyer, toward the liberal end of the two-party divide," said Jacob Goldin, an economist and incoming law professor at Stanford and a co-author of the working paper. "He would be the new median justice on the court."
Still, using clerks as a proxy for judges isn't a perfect system. While most judges hire clerks whose ideologies match their own, and law clerks' political beliefs can even end up influencing the outcome of court decisions, clerks' ideologies don't always match the judges' they work for.
Scalia was famous for hiring a liberal clerk to mix it up with his conservative choices, which would have pushed him to the right on this measurement — at least, Goldin says, until he started hiring solely conservative clerks, around 2004.
Not everything can be measured
The real problem with these measurements, though, is that they don't tell us much beyond what we already knew: President Obama is a center-left president who is not going to turn down a chance, however slim, to shift the Supreme Court in a more liberal direction.
And if you take as a given that Obama was going to appoint a liberal or moderate justice rather than a conservative, there's only so much more that a single measurement of a justice's ideology can tell you about their contributions to the court. It makes sense to summarize the ideology of members of Congress: Most Americans aren't single-issue voters, Congress votes on hundreds of measures each year, and there are 435 members of Congress. It's useful to understand where they rank in relation to one another.
But there are only nine justices. They aren't voting on dozens of laws, but setting precedents on a smaller number of very different, very important topics. Their votes on a single issue — whether it's abortion or campaign finance — could well be the most important fact about their judicial careers.
The creators of these models acknowledge that they miss some things. "Garland was a prosecutor, so he may be substantially more conservative" on criminal justice issues, Segal said. "A lot of what the Court does involves criminal cases. it’s probably the largest part of their agenda."
These distinctions might seem obvious, but they really matter. Attempting to measure the ideology of a Supreme Court justice as if she were a member of Congress means conflating and flattening their views.
Scalia voted with the Court's liberal wing on flag-burning, search and seizure, and restrictions on violent video games. Those votes don't make him a moderate; they were another expression of his views on the Constitution. They just illustrate that it's difficult to perfectly map a Supreme Court justice onto a left-right scale.