According to the analysis, authored by University of Illinois College of Law professors Robin Bradley Kar and Jason Mazzone, Senate Republicans’ “major departure from more than two centuries of historical tradition” poses the risk that “no future Supreme Court Justice will be appointable unless the President and the Senate are of the same political party.”

As the authors explained, circumstances similar to President Obama’s -- where an elected president is presented with a Supreme Court vacancy prior to the election of his successor -- have occurred 103 times in U.S. history. In each of those instances, the Senate voted to confirm a judge nominated by that president to fill the vacancy.

Kar and Mazzone warn that Republicans’ insistence on rejecting this longstanding historical precedent creates “historic, pragmatic, and constitutional risks” and urge that “Senate Republican leaders should reconsider their current plan” (internal citations removed, emphasis original):

In particular, history suggests that while there may be no general duty on the part of the Senate to provide advice and consent with respect to every nomination to a federal office that a President may make, the Supreme Court presents a special case. As we show, the Senate has only refused to consider a President’s Supreme Court nominations in the highly unusual circumstance where the nominating President’s status as the most recently elected President has been in doubt. Once this fact is recognized, it will become clear that the Republican plan is historically unprecedented and entails more extensive pragmatic and constitutional risks than have thus far been recognized. These risks may well outweigh the originally perceived benefits of the plan, even to Senate Republicans.

[…]

Part I therefore begins with a close look at the entire relevant history. By examining every Supreme Court appointment process in U.S. history, we uncover a principled but underappreciated distinction between cases where the Senate has provided advice and consent on particular Supreme Court nominees—by considering them (and either confirming, rejecting, or resisting them on the merits using a wide array of senatorial procedures)—and cases where the Senate has sought deliberately to transfer a sitting President’s complete Supreme Court appointment powers to a successor. We show that tactics of the latter kind have always been limited to the unusual circumstance where there were contemporaneous questions concerning the status of the nominating President as the most recently elected President. More specifically, all such cases involved a President who either (a) attained office by succession rather than election or (b) began the nomination process after the election of his successor. Neither circumstance applies to President Obama’s nomination of Judge Garland. Moreover, bracketing these highly unusual circumstances, we show that there have been 103 prior cases in which—as in the case of Obama’s nomination of Garland -- an elected President nominated someone to fill an actual Supreme Court vacancy and began the nomination process prior to the election of a successor. In all 103 cases, which go back all the way to the earliest days of the Republic, the sitting President was able to both nominate and appoint a replacement Justice -- by and with the advice and consent of the Senate, and regardless of the senatorial rules and procedures in place. Hence, in none of the 103 cases that most closely resemble the current controversy has a sitting President been unable to fill an existing Supreme Court vacancy with some nominee.

The historical rule that best accounts for the entire history of Supreme Court appointments is thus the following: Although the Senate has the constitutional power to provide advice and consent on particular Supreme Court nominees (and hence to reject or resist individual nominees on the merits), the Senate may only deliberately transfer one President’s Supreme Court appointment powers to an unknown successor -- as Senate Republicans are currently attempting to do with their plan -- if there are contemporaneous questions about the status of the nominating President as the most recently elected President. There are no such credible questions about President Obama’s status. Hence, while Senate Republicans have framed their opposition to the nomination of Judge Garland as hewing to historical practices, their plan in fact presents a major departure from more than two centuries of historical tradition.

[…]

The logical terminus of the current Republican plan may also be that no future Supreme Court Justice will be appointable unless the President and the Senate are of the same political party. Such a result can only lead to a more -- rather than less -- politicized appointment process and, ultimately, to a more politicized Court.

[…]

In order to avoid the historic, pragmatic, and constitutional risks we set forth, Senate Republican leaders should reconsider their current plan. They should not breach a tradition that goes back more than two centuries and began in the earliest days of the Republic. They should instead do what has always been done in similar circumstances. They should proceed to full Senate consideration of Judge Garland or any other nominee that President Obama puts forth in a timely manner.

h/t Geoffrey R. Stone