When the Supreme Court hears cases, delivers opinions or even poses for a group photo, Chief Justice John Roberts is the man in the middle — literally.

With the retirement of Associate Justice Anthony Kennedy, the court’s most influential member by virtue of his “swing vote” status, Roberts will move to the middle figuratively as well.

To replace Kennedy, President Trump is determined to nominate someone in the mold of the late Justice Antonin Scalia and his successor, Justice Neil Gorsuch, who won the president’s nod last year. Roberts, to the occasional chagrin of conservatives, is a bit more flexible than that.

This, after all, is the chief justice who rescued President Obama’s signature health care law from extinction in 2012, when even Kennedy voted to scrap it. On rare occasions before and since — though not so much in the term just ended — he has cast his lot with the court’s liberal justices.

But after 13 years on the court as chief justice, Roberts, 63, is fairly set in his jurisprudence. So if Trump’s nominee becomes the 14th justice named by a Republican president out of the last 18, the middle of the court finally should shift to the right.

“There’s little doubt right now that with Kennedy’s departure, the chief becomes the center of the court,” says Richard Lazarus, a professor at Harvard Law School and Roberts’ roommate there in the 1970s. “It doesn’t mean the chief changes. It just means the center changes.”

Under Kennedy and former justice Sandra Day O’Connor, who retired in 2006, the court’s center of gravity shifted depending on the subject. They often voted with liberals on abortion, affirmative action, gay rights and other social issues.

Roberts has sided with liberals on some issues, but they are less ideological. Like Kennedy, he’s a stickler for freedom of speech. Like Scalia, he often defends the rights of criminal suspects. This term, he penned the 5-4 verdict that police need a warrant to track a person’s prior movements from their cellphone locations over weeks or months.

While the court’s other three conservatives — Clarence Thomas, Samuel Alito and Gorsuch — are further to the right, Roberts and Kennedy voted together 90 percent of the time in the term that just ended.

But the similarity pretty much ends there. Unlike Kennedy, Roberts has been a firm opponent of abortion, affirmative action and gay rights, at least in his rulings.

He sided with the court’s majority in the landmark Citizens United case that allowed for unlimited independent corporate spending on elections, and he wrote the decision striking down the key section of the Voting Rights Act. When Kennedy’s ruling expanded same-sex marriage nationwide in 2015, Roberts spoke from the bench in dissent, the only time he has done so.

“On the most hot-button, controversial issues — affirmative action, abortion, gay and lesbian rights, the Second Amendment — Roberts is with the conservatives 100% of the time,” says Erwin Chemerinsky, dean of the University of California-Berkeley School of Law.

“Roberts is now at the center of the court, but that just reflects how conservative the Supreme Court is going to be,” says Brianne Gorod, chief counsel at the liberal Constitutional Accountability Center, who led a study of the Roberts Court when it reached the 10-year mark in 2015. 

Roberts’ impending ascension to both the literal and figurative center of the court represents an about-face from two years ago. Then, it briefly looked like President Obama’s nomination of federal appeals court Judge Merrick Garland to replace Scalia could relegate the chief justice to the conservative minority.

Senate Republicans’ refusal to consider Garland, followed by Trump’s election and Gorsuch’s confirmation, kept conservatives in the majority. Kennedy’s retirement solidifies that. And with Thomas the oldest of the conservatives at 70, they could reign supreme for another decade or more.

‘Committed incrementalist’

There are several reasons why Roberts may stand apart from the crowd, however:

• He favors incremental changes in the law, rather than swinging for the fences, as Kennedy sometimes did on issues such as campaign financing and same-sex marriage.

“He was the middle of the court, but he wasn’t a moderate. He was an activist,” Lazarus says of Kennedy. “Roberts is a committed incrementalist.”

“It’s my job to call balls and strikes, and not to pitch or bat,” he assured lawmakers during his confirmation hearings in 2005. The Senate rewarded him with a 78-22 vote, a far better percentage than the justices who have followed.

• He respects the court’s precedents, which could stymie or at least stall conservatives eager to overrule the 1973 Roe v. Wade decision that legalized abortion. (Roberts did vote with the other conservatives this week to overrule a 1977 decision that had allowed public employee unions to collect fees from non-members.)

Bolstered by Kennedy’s successor, conservative state officials and interest groups are likely to target other precedents, such as a 1997 ruling that granted federal agencies broad discretion to interpret regulations. That could test Roberts’ resolve.

“They’re going to be more aggressive. They’re certainly going to be more emboldened,” says Lee Epstein, a Supreme Court expert at Washington University in St. Louis. “You have a justice in the middle who’s not going to flip to the left very often.”

• He is deeply concerned about the court’s image, from appearing nonpartisan to letting litigators get a word in edgewise between justices’ rapid-fire questions. During oral argument on a challenge to state election maps drawn for partisan advantage, Roberts fretted about how judicial policing could be perceived.

“That is going to cause very serious harm to the status and integrity of the decisions of this court in the eyes of the country,” he said.

“The chief justice does care about the institutional legitimacy of the court,” Gorod says. “He does care about how judges are perceived.”

The question moving forward is whether Roberts’ cautious instincts will stand in the way of a conservative juggernaut. Most liberals fear not.

“This is what conservatives have been dreaming about since Richard Nixon ran for president,” Chemerinsky says. “This is going to be the most conservative court that there’s been since the 1930s.”