Mark Tushnet chairs the advisory board of Take Back the Court, an organization that advocates for structural reform of the Supreme Court. He is also the author of the forthcoming book, “Taking Back the Constitution: Activist Judges and the Next Age of American Law.” Harvard Law Today recently emailed with Tushnet about the possibilities for, and potential pitfalls of, any effort by a potential incoming Democratic majority to pack the Supreme Court.

Harvard Law Today: How is the number of Supreme Court justices decided? In other words, why nine?

Mark Tushnet: The number of Supreme Court justices is set by statute and has varied from six to 10 (briefly, during the Civil War era). It’s been set at nine since 1869, and many constitutional scholars think that the failure of FDR’s so-called “Court-packing” plan in 1937 created a convention that the Court’s size shouldn’t be changed if the purpose is to change the tenor of its decisions.

HLT: You write that some commentators, scholars and former Democratic presidential candidates have expressed openness to increasing the number of Supreme Court justices. Why?

Tushnet: There are some facts about the Court today that suggest to Democrats that something has gotten out of hand. Despite the fact that Democrats have won the presidency about as often as Republicans, the last time there was a chief justice nominated by a Democratic president was in 1953, and the last time a majority of the Court’s justices were nominated by a Democratic president was in 1969. The fact that Supreme Court seats open up either randomly or, more troublingly, because sitting justices time their retirements so that “their” party can replace them has led some Democrats to believe that the traditional alignment between the overall political system and the Court—when looked at over a decent (say 10-year) period—has come unstuck, and that they should consider whether or how to reestablish that alignment.

HLT: Can you remind us about the last time a U.S. president attempted to “pack” the Court?

Tushnet: In 1936, the Supreme Court issued a number of decisions invalidating central features of the New Deal programs sponsored by President Franklin Delano Roosevelt, and FDR and his supporters feared that more was to come (including the invalidation of the National Labor Relations Act and the Social Security Act, probably the key New Deal programs). To forestall that, FDR proposed to add up to six additional justices to the Court, disingenuously presenting the plan as a “good government” proposal to improve the Court’s workings by adding one justice for each justice over the age of 70½.

The plan ran into strenuous opposition in the Senate, though (in my view) its success was touch-and-go until the end. The plan had the support of the powerful Senate majority leader Joseph Robinson, whom FDR had promised to appoint to one of the new positions, and it failed only after Robinson’s unexpected death during the very hot summer of 1937. (I discuss much of this in my forthcoming history of the Supreme Court during the 1930s, to be published next year as part of The Oliver Wendell Holmes Devise History of the Supreme Court