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Roberts Is The New Swing Justice. That Doesn’t Mean He’s Becoming More Liberal.

This Supreme Court term belonged to John Roberts. The chief justice was in the majority in nearly every case. And he quite literally had the last word, as he wrote the opinion for the last two cases released this term, which dealt with President Trump’s much sought-after financial records. The rulings were largely interpreted as a rebuke to Trump, and considering Roberts unexpectedly joined the liberals in several other cases this term, some have speculated that the conservative chief might be moving to the center.

But is Roberts actually becoming more liberal?

New data from Supreme Court researchers indicates that Roberts is firmly at the center of the court. According to this year’s Martin-Quinn scores, a prominent measure of the justices’ ideology, there is an 82 percent chance that Roberts was the median justice in the term that just wrapped. However, as the chart below shows, there is some uncertainty about where he actually falls — or how much daylight exists between Roberts’s ideological position this term and the positions of Justices Brett Kavanaugh and Neil Gorsuch.

But moving to the center of the court does not mean Roberts is becoming a liberal or even a centrist. Yes, he joined the liberals in several high-profile cases, and according to justice pairing data analyzed by Adam Feldman for SCOTUSBlog, he aligned with Justice Elena Kagan, a liberal, more frequently than with fellow conservative Justice Clarence Thomas. But many of the cases where Roberts sided with the liberals were limited in scope or temporary in effect. Roberts also helped push forward several long-held conservative goals — including dramatically expanding the definition of religious liberty — as the pivotal vote in many cases.

Roberts has long been perceived as a conservative, both ideologically and temperamentally — a justice who would prefer to gradually chip away at liberal precedents rather than dispatching them with one swift blow. And on an increasingly conservative Supreme Court, it’s not hard to see how that incrementalist sentiment — combined with a fear of what would happen if the court moved too quickly out of the mainstream — might lead Roberts to some unexpected places and deliver some unwelcome losses to the conservative legal movement. But that doesn’t mean he’s changing in any fundamental way, or that he won’t continue to quietly steer the court in a conservative direction. “People seem to see Roberts moving to the center of the court and assume that he’s becoming more liberal,” said Melissa Murray, a law professor at New York University. “I would read it a different way — that the court is moving to the right.”

The idea that Roberts is becoming more liberal didn’t come out of nowhere. Over the past few years, his ideological position on the court — as measured by the Martin-Quinn scores — has inched toward the center. In 2005, when he joined the court, he was basically indistinguishable ideologically from Justice Samuel Alito, who was appointed around the same time. Now, however, Alito is probably the second most conservative justice on the court, while Roberts is the fifth most conservative.

The easiest way to interpret that trend is simply to conclude that Roberts is becoming more liberal. After all, he wouldn’t be the first Republican-appointed justice to move left over time. In perhaps the most dramatic example in modern Supreme Court history, a Nixon appointee, Justice Harry Blackmun, started off conservative but was the court’s most liberal member by the time he retired in 1994.

Other factors could explain Roberts’s shift, though, starting with a limitation of the Martin-Quinn scores themselves. The scores are estimates produced by a model based on how the justices vote — they are not a direct window into what the justices actually believe or what’s motivating their votes. The scores also can shift as the composition of the court changes, and the court is still adjusting after the previous longtime swing justice, Anthony Kennedy, retired and was replaced in 2018 by Kavanaugh, who has so far proven to be much more reliably conservative.

[Related: The Supreme Court’s Big Rulings Were Surprisingly Mainstream This Year]

Think about it this way: One justice has to be in the middle of the court. So when Kennedy retired and was replaced by a more conservative judge, someone else had to take his place in the center. In this case, that somebody was Roberts. “It could be the case that Roberts is actually drifting left,” said Tom Clark, a political science professor at Emory University. “But it could also be an artifact of the statistical model trying to sort out what happens to the space when you add a new person. At this point, we don’t know which one it is.”

The model also retroactively updates justices’ scores for past years at the end of each term. The changes can be substantial with new justices, since the model has little data about their positions when they first join the court. Case in point: In last year’s Martin-Quinn data, Kennedy was deemed to be the most likely median justice in 2017 and Kavanaugh took the role in 2018, not Roberts. But with the addition of 2019 data, Roberts is now estimated to have actually been the likely median in both years. That’s partly because we now have a better understanding of how Kavanaugh tends to rule; it also reflects the a fairly high probability that Roberts was already the median justice in the 2017 term, because Kennedy hardly swung at all in his final year on the court.

[Related: John Roberts Will Probably Be The Supreme Court’s Next Swing Justice]

Meanwhile, it’s also possible that Roberts just appears to be moving to the left because the kinds of cases that make it to the court are shifting. This effect is especially difficult to measure and the Martin-Quinn scores can only account for it in a limited way. But Clark said if the types of cases being brought before the court are changing, that could matter a lot to how liberal or conservative each justice’s rulings really are. Because it could be that the Trump administration and conservative legal advocates, emboldened by the solid slate of conservatives on the court, are simply pushing Roberts to move to the right faster than he’s willing to go.

Take one high-profile case from this term, where the justices considered a Louisiana abortion restriction that was functionally identical to a Texas law the court had struck down in 2016. In the previous case, Kennedy — who over the course of his career was ideologically unpredictable on a handful of high-salience issues, including the abortion, affirmative action and the death penalty — voted with the liberals against the Texas law. This year, though, Roberts broke the tie, saying that while he still disagreed with the 2016 ruling, he felt he had to adhere to the precedent. That doesn’t mean Roberts’s fundamental stance toward abortion changed, though. Instead, the change in the court’s composition put him in a situation where institutional considerations — like not wanting to overturn a recent precedent on an extremely hot-button issue four months before a presidential election — may have trumped his own ideological preferences.

[Related: The Supreme Court Struck Down A Louisiana Abortion Law. Here’s Where The Fight Could Head Next.]

That’s significant because in the vast majority of cases, Roberts appears to be basically as conservative as he’s ever been. According to The Supreme Court Database, a clearinghouse for data about the court, the share of opinions where he voted in a conservative direction hasn’t actually changed much in the past few years — when Kennedy’s departure and the addition of Trump’s more solidly conservative appointees gave Roberts an increasingly pivotal vote — compared to his opinions between the 2005 and the 2017 terms. (This data is not yet available for the term that just ended.)

Roberts hasn’t really become more liberal

Share of Roberts’s votes that were coded as conservative, before and after the 2016 Supreme Court term

Pre-Trump Post-Trump
Cases Votes Conservative Rulings Votes Conservative Rulings Diff.
Close 198 81.8% 38 78.9% -2.9
All 914 58.2 137 55.5 -2.7

“Pre-Trump” includes case data for the 2005-2016 terms, while “post-Trump” covers the 2017 and 2018 terms. The 2016 term is counted as pre-Trump because it started before Trump was elected, but it ended in 2017. “Close cases” are defined as those in which the majority was four or five and the minority was three or four.

Source: The Supreme Court Database

In other words, Roberts is still very conservative. (For the record, so was Kennedy.) But several experts told us it’s possible that in Kennedy’s absence, Roberts may be increasingly willing to rule narrowly with the liberals in certain high-stakes cases. Part of his motivation is likely that as chief justice, he feels a responsibility to ensure that the court maintains its reputation as an even-handed institution.

This year was a perfect storm for a chief justice trying to keep the Supreme Court from being dragged into the muck of partisan politics, too. “The country is deeply polarized, we’re heading into a presidential election, there’s a pandemic, an economic crisis, significant social unrest,” said Marin Levy, a professor at Duke Law who studies chief justices. “This is a moment where it’s critical to someone like Roberts that the public maintain its faith in the court.” And in fact, even though this term’s docket was full of hot-button issues, the court’s rulings were largely in step with public opinion, thanks in part to Roberts’s willingness to join the liberals.

[Related: Justice Kennedy Wasn’t A Moderate]

So if Kennedy’s forays to the left were motivated by a couple of issues on which his views were more liberal than the rest of the conservative bloc, like gay rights and sometimes abortion, Roberts’s recent swings appear to be be driven by more strategic — and even political — considerations. “He’s concerned about maintaining his own power and the power of the court,” said Leah Litman, a professor of law at the University of Michigan. It was perhaps a sign of Roberts’s success that some of the biggest conservative victories this term mostly flew under the radar, such as when the conservatives continued to expand the circumstances under which religious schools can qualify for public funding, building on a case from 2017. Litman and others said that Roberts could follow a similar blueprint for eroding something like abortion rights in the future. Rather than overturning precedents outright, he might prefer to whittle away at abortion access by allowing states to pass a patchwork of restrictions, until landmark precedents on abortion eventually become functionally hollow.

Right now, of course, Roberts is still the closest thing we have to a swing justice. But he’s not really a wild card — especially compared to Kennedy, who was genuinely unpredictable on a handful of issues, including abortion. Clark said a better description for Roberts might be the “pivotal” justice, or the person with the power to broker compromises between left and right, allowing him to determine the court’s direction. That moniker is especially apt given that Roberts was so frequently in the majority this term. At SCOTUSBlog, Feldman suggested calling him the “anchor” justice for that reason. The fact that Roberts is chief justice gives him additional power when he votes with the majority, too: He gets to assign the opinion to a specific justice, and that can do a lot to shape the breadth and impact of the final ruling.

[Related: The Supreme Court Put DACA’s Fate In The Hands Of Voters]

One thing does seem clear: Roberts is now by far the most powerful person on the Supreme Court. And he is not willing — at least not yet — to let his fellow conservatives veer sharply to the right. But his occasional votes with the liberals shouldn’t obscure the fact that he’s still a very conservative justice overall. As with Kennedy, the handful of times he swings to the left may come to define his career. And this term he’s certainly proved that Trump — and conservative legal advocates — can’t expect him to rubber-stamp any argument they lay at his feet. But when he does swing, it will likely be political and institutional factors, not a shift in his ideology, that guide his vote. And that means liberals really can’t rely on him to rule their way in the future.

FiveThirtyEight Politics: Conservatives didn’t get the SCOTUS they wanted this term

Amelia Thomson-DeVeaux is a senior editor and senior reporter for FiveThirtyEight.

Laura Bronner is a senior applied scientist at ETH Zürich and FiveThirtyEight’s former quantitative editor.

Elena Mejía was a visual journalist at FiveThirtyEight.