Last Saturday, Supreme Court Justice Ruth Bader Ginsburg celebrated her 81st birthday, and soon thereafter she got her customary "gift" — a public call for her to retire from the bench. She couldn't have been too surprised by the unsolicited recommendation, as something quite similar took place when she turned 80 last year.

Although Justice Ginsburg may be the least politically conservative member of the high court, the calls for her resignation have come primarily, if not exclusively, from liberals. Their thinking is this: Should she wait any longer than the end of the current term in June to step down (or be carried out), the chances a more conservative justice will take her place — and the ideological balance of the court will be tipped in that direction — are much greater.

At least that was the reasoning presented by Erwin Chemerinsky, the influential and widely respected dean of the University of California-Irvine School of Law. Writing last week in the Los Angeles Times (in a commentary republished at startribune.com/opinion), he reasons the deadline is not just President Obama's departure from the White House in 2017 and the chance a Republican will be elected to succeed him but the real possibility that the GOP will gain a majority in the U.S. Senate this year and block any liberal nominee.

Chermerinsky, 60, makes a valid point. Historically, the Senate does not filibuster Supreme Court nominees (the only exception being the manner in which Justice Abe Fortas was blocked from becoming the chief justice), but a majority rejecting a nominee on the basis of ideology? That does happen, and in the Tea Party era, Republicans like Texas Sen. Ted Cruz look to be itching for such a fight. If Justice Ginsburg wishes to protect her legacy, resigning now would make some sense. On any number of fronts important to progressives, including gay marriage, recent 5-4 decisions have depended on four liberal justices being joined by Justice Anthony M. Kennedy. Make it three liberal justices, and suddenly that Kennedy swing vote no longer swings a majority.

But it's also exactly wrong to expect her to view her work through such a political prism. Not only because Justice Ginsburg, despite surviving two bouts with cancer, appears to be in good health, maintains a robust schedule and, by all accounts, retains her keen intellect, but because it seems fundamentally wrong to expect a Supreme Court justice to make such ideologically driven calculations about future courts and appointments.

Ginsburg was appointed in 1993 by President Bill Clinton to the court for as long as she chooses to serve. Under the Constitution, a justice can be removed from office involuntarily only by impeachment, something that has never happened (although Justice Samuel Chase was impeached by the House in 1805, he was subsequently acquitted by the Senate). The purpose of such a lifetime appointment is to keep the court independent and shield its members from interference from either the executive or legislative branches.

What is a call to resign now but another form of political interference? There's also some irony to any expectation that the well-regarded Ginsburg, only the second woman ever appointed to her job and one who argued for equal rights as a onetime general counsel to the American Civil Liberties Union, would be under such pressure when so many of her peers and predecessors have not faced such a call. Critics should recognize that she's unlikely to accommodate them and step down; last year, she publicly vowed to remain on the court regardless of who is in the White House.

Admittedly, the stakes in Supreme Court nominations are exceptionally high, and their impact can last for decades. As Chermerinsky points out, had Republican U.S. Sen. John McCain been elected president in 2008, he likely would have chosen successors to David Souter and John Paul Stevens who would have tipped the balance of the court to the conservative side already. But that is exactly the point of elections, and voters ought to make the composition of the Supreme Court a major consideration in the 2016 presidential race and perhaps in this year's Senate races as well. It should not be the business of Supreme Court justices to try to manipulate the appointment process in the name of politics or even legacy.