With Kennedy’s Retirement, the Supreme Court Loses Its Center

Justice Anthony M. Kennedy announced Wednesday that he would retire from the Supreme Court, leaving a second seat for President Donald Trump to fill during his short time in office. Kennedy, the court’s crucial swing vote, has served on the court for 30 years.

For much of his tenure, Kennedy has been the median justice, falling in the court’s ideological center, according to a measure based on voting patterns. He was nominated by President Ronald Reagan, a Republican, in 1988. And while Kennedy has been considered a member of the court’s more conservative bloc, he became slightly more liberal in recent terms.

This year has been an exception, and his current vote ranking is nearly indistinguishable from that of Chief Justice John Roberts.

From 1937 to today, 19 justices have been the median justice, but only three maintained that position for 10 or more years during their tenure. Justice Sandra Day O’Connor held the role for 10 years, Justice Byron White for 15, and Kennedy for 18.

Kennedy has been an essential figure in forming a majority on the court. He voted on the winning side of close decisions 76 percent of the time over his career, far more often than any other justice he served with except for Justice Neil Gorsuch, who joined the court last year.

Kennedy joined both the conservative and liberal blocs of justices to provide a decisive vote in several landmark cases.

“Kennedy is at or near the top on almost all measures of power or influence,” said Lee Epstein, a political scientist at Washington University in St. Louis. “I would say that he is among the most powerful justices since at least 1937.”

Kennedy was one of the most crucial median justices in building a majority because the distance between him and the justices on either side of him ideologically was so large in most of the years in which he had that role.

When the justice in the middle is ideologically distinct, it’s harder for either side to form a majority coalition, which makes the median justice central in not just choosing a side but shaping the contours of the court’s opinion.

From 1993 to 2005, Kennedy shared the center of the court with O’Connor. When a liberal and conservative camp formed during this time, neither side was restricted to Kennedy as the swing vote, because O’Connor could also be called upon to form a majority — a dynamic that diluted the power of both.

Few justices have continued their tenures on the court after the age of 80, and only 11 justices have served while they were older than Kennedy. Justice Oliver Wendell Holmes tops the list, retiring in 1932 at 91 years old.

Ruth Bader Ginsburg, 85, is the oldest member of the current Supreme Court but has given no public hint of a retirement. “As long as I can do the job full steam, I will be here,” she said in January.

Roberts will become the new median justice if Trump nominates someone more conservative than the chief justice. Since 1937, no chief justice has also been the median justice.

Divisive Supreme Court decisions are more likely to be re-examined — and possibly overturned — when a court changes.

“Because Kennedy drifted right this term, he and Roberts shared the median spot,” Epstein said. “For this reason, the 2017 term provides a good indication of what a post-Kennedy court might look like: many 5-4 decisions with the four Democratic appointees losing in the vast majority.”