Brett Kavanaugh is uncommonly partisan, research shows

Judges, particularly those on the Supreme Court, are expected to sit above the partisan fray. But Brett Kavanaugh, whom President Donald Trump nominated to succeed Justice Anthony Kennedy on Monday night, is much like the man who selected him — highly divisive in his decisions and rhetoric. According to a deep, data-driven survey of his writings from the bench, he is an uncommonly partisan judge, even compared with other federal appeals court judges.

On the circuit court, Kavanaugh tended to dissent more often along partisan lines than his peers, according to our research. He justified his decisions with conservative doctrines far more than his colleagues, citing politicized precedents consistent with other Republican-appointed judges, invoking the original Articles of the Constitution (consistent with the originalist jurisprudence favored by conservative jurists) and using the language of economics and free markets. What's more, Kavanaugh's divisiveness ramped up during campaign season: He disagreed with his colleagues more often before elections, suggesting that he feels personally invested in national politics.

These findings stem from our work as social scientists who use data to understand the U.S. legal system and the decisions of judges. Although we can't read their minds, new data technologies allow us to sift through a judge's record for insights into his or her worldview and political values. Through his published decisions on the D.C. Circuit Court (where he has reviewed cases since 2006), Kava-naugh provides ample material for this type of data-driven investigation.

In federal appeals courts, cases are usually decided by three-judge panels. Across the D.C. Circuit during Kavanaugh's tenure there, 3 percent of the votes were dissents. But Kavanaugh cast a dissenting vote 7 percent of the time. When Kavanaugh authored the opinion, 14 percent of the time the copanelists dissented against him, compared with only 10 percent of opinions that provoked dissents when he wasn't the author. In contrast to this rift-making, Justice Neil Gorsuch — as well as previous nominees rejected for being divisive, such as Merrick Garland and Robert Bork — generated more agreement than Kavanaugh relative to their peers on the opinions that they wrote.

We also found that he was extremely polarizing in his votes. We measured how dissents vary with the party affiliation of the president who appointed judges. (For the sake of our research, judges elevated by a Republican president are "Republicans," and vice versa.) Judges who tend to dissent mostly against those appointed by the opposing party's president contribute to "vote polarization." When sitting with two panelists appointed by Democrats, Kavanaugh dissented 19 percent of the time; in other cases, he dissented 5 percent of the time, which is nearly double the rate of his colleagues. Kavanaugh's vote polarization is especially clear in cases relating to constitutional, civil rights and due process law. (In a recent abortion case, for example, he dissented against the Democrat-controlled majority ruling that guaranteed an undocumented immigrant's right to an abortion while in state custody.) Gorsuch and Bork, by contrast, did not display the same degree of vote polarization. Garland was actually more likely to cross party lines than his D.C. Circuit colleagues did.

Another way that dissents can provide evidence of polarization is when they respond to external political factors. A forthcoming paper by one of the authors, Daniel L. Chen, with Carlos Berdejó, shows that circuit court judges tend to dissent more in the run-up to presidential elections, consistent with a (perhaps subconscious) political cheerleading motive or affect related to partisan identity. Kavanaugh was an exemplar of this trend. Beginning the February before a presidential election, Kavanaugh dissented 15 percent of the time; at other times, he dissented just 5 percent of the time. (Other judges in his circuit dissented 3 percent right before an election and 2 percent at other times.) Kavanaugh's "electoral dissent" is especially prevalent in highly political topics such as economic regulation, constitutional law and due process cases. Gorsuch, Garland and Bork were significantly less affected by external politics.

Kavanaugh is a partisan warrior even in his legal citations. When justifying his rulings, Kavanaugh tends to cite precedents that have a partisan Republican slant: In Adeyemi vs. District of Columbia, putting limits on employee discrimination claims, he quoted conservative precedent articulating "an employer's unfettered discretion" over hiring and firing. He often cites original Articles of the Constitution, especially Article II, which is associated with originalism and expanded executive power. He also invokes more economics language than his colleagues, using market-oriented arguments associated with deregulatory policy goals. In United States vs. Bullock, for instance, he employed a risk-harm calculus to determine the propriety of police searches.

These partisan views also emerge in a sentiment analysis of Kavanaugh's opinions. Using the relative positive or negative sentiment of his language (words like "favorable" and "warm" contrast with words like "unfavorable" or "cold"), we found that Kavanaugh tended to speak positively of conservatism and negatively of liberalism. More so than his colleagues, he expressed dislike toward government (Congress and the federal government) and working class groups (labor unions and farmers).

Kavanaugh's dissent in Agri Processor Co. Inc. vs. NLRB illustrates his unenthusiastic attitude toward labor: "Their immigration status apparently unbeknown to their employer, illegal immigrant workers voted in a union election and affected the election's outcome. The employer later discovered that the workers were illegal; terminated them as required by federal immigration law; and sought to overturn the tainted union election."

A broader comparison of his writing style to sitting Supreme Court judges shows that Kavanaugh's opinions are closest to Samuel Alito's, a Bush appointee who is known to be on the conservative fringe. But as a circuit judge, Alito was less extreme than Kavanaugh in terms of dissents, vote polarization, electoral dissents and citing partisan precedents.

Kavanaugh is not your average justice. On the evidence derived from the content of his decisions, he is more radical than his colleagues.

Elliott Ash is an assistant professor of law, economics and data science at ETH Zurich. Daniel L. Chen is a professor at the Toulouse School of Economics and a research associate at the Institute for Advanced Study in Toulouse. They wrote this article for the Washington Post's PostEverything blog.