Supreme Court justices say they do not act politically when they decide cases. But they freely admit to taking account of politics in deciding when to retire. Most justices, for instance, try to step down under politically like-minded presidents.

“That’s not 100 percent true,” Chief Justice William H. Rehnquist said in 1999, six years before he died, “but it certainly is true in more cases than not.”

Such political calculations are perfectly proper, he said, as “deciding when to step down from the court is not a judicial act.”