In nearly 11 years as a federal appeals court judge, President Obama’s choice for the Supreme Court, Sonia Sotomayor, has never directly ruled on whether the Constitution protects a woman’s right to an abortion. But when she has written opinions that touched tangentially on abortion disputes, she has reached outcomes in some cases that were favorable to abortion opponents.

Now, some abortion rights advocates are quietly expressing unease that Judge Sotomayor may not be a reliable vote to uphold Roe v. Wade, the landmark 1973 abortion rights decision. In a letter, Nancy Keenan, president of Naral Pro-Choice America, urged supporters to press senators to demand that Judge Sotomayor reveal her views on privacy rights before any confirmation vote....

Presidents have miscalculated in their assumptions about the abortion views of Supreme Court nominees before. When the first President Bush nominated David H. Souter in 1990 to fill the seat that Judge Sotomayor would assume if confirmed, Mr. Souter was known as a “stealth nominee” with no paper trail on abortion.

But conservative and liberal advocates alike believed that Justice Souter would vote to overturn Roe v. Wade, so much so that abortion rights advocates protested outside his confirmation hearing with signs reading “Stop Souter, or Women Will Die.” Then, two years later, Justice Souter shocked the political world by voting to uphold abortion rights.