A no-compromise posture may be heartening for activists who worry about appearing timid on the issue at a time of such uncertainty and anxiety. But prominent allies to the cause have grown increasingly worried that the impulse to take a hard line has weakened their efforts politically and legally, and left them vulnerable to conservatives who eagerly portray them as out of step with the sentiments of most Americans.

“There’s always this sense that we can’t say anything that would create doubt about abortion,” said Frances Kissling, president of the Center for Health and Social Policy. “And the current situation hardens people’s sense of absolutism.”

Ms. Kissling, who is often called “the philosopher of the pro-choice movement,” said that to gloss over the complexity and morality of ending a pregnancy is to deny the reality that women experience. “I think that if you do not express any moral doubt about any aspect of abortion nobody trusts you,” she said. “You are so far from the sensibility of women who actually have abortions.”