My colleague Everett Ladd and I have been reviewing polls conducted over the past 25 years on abortion. What's astonishing about this vast collection of data is its stability.

We're often told that public opinion is fickle and easy to manipulate. Nothing could be further from the truth on abortion. Opinion on the issue has not changed in 25 years.

That isn't to say people's beliefs about it are one-dimensional. They're not. Most Americans hold within themselves deeply contradictory views about abortion. Large majorities consistently say that abortion should be a decision between a woman and her doctor. But significant numbers also say that abortion is an act of murder.

Americans want abortion to be legal, but not under all circumstances. In 1975, 21 percent of those surveyed by Gallup said abortions should be legal under any circumstances, 54 percent only under certain circumstances, and 22 percent wanted them to be illegal in all circumstances.

The question has been asked 22 times since then. When Gallup last repeated the question in November 1997, the results (26, 55, and 17 percent, respectively) were very similar to those from 1975.

In 1994, Gallup began asking those who took the middle position--legal only under certain circumstances--a follow-up question. These people were asked whether abortion should be legal in most circumstances or only in a few circumstances. This follow-up question has been asked four times, and each time, far more of the people in the middle have said abortion should be legal "only in a few circumstances" than have said it should be legal "in most circumstances."

What kind of restrictions do Americans support? Again, we turn to Gallup. In 1992 and 1996, virtually identical numbers of people said they supported laws requiring women seeking abortions to wait 24 hours before having the procedure done (73 percent in January 1992 and 74 percent in July 1996); a law requiring doctors to inform patients about alternatives (86 percent in each year); a law requiring parental consent for a woman under 18 (70 and 74 percent); and a law requiring spousal notification (73 and 70 percent).

When Gallup asked teens themselves about whether parental consent should be required to get an abortion, 78 percent said it should.

Americans believe that abortion should be legal in the first three months (64 percent), but they are not in favor of second-trimester abortions (24 percent say they should be generally legal; 65 percent, generally illegal), and they reject third-trimester abortions by an overwhelming margin (13 to 82 percent), according to Gallup's August 1996 poll.

In February 1997, the Field poll asked Californians a very similar question, and their answers were almost identical to Gallup's national ones. Sixty-two percent of Californians approved of allowing abortions in the first three months, 26 percent approved of allowing them during the second three months, and 14 percent in the last trimester.

When people believe contradictory things about an issue, they tend to pull away from it. That's what has happened on abortion. Only around 10 percent say that this issue is the most important one to them in casting their presidential vote.

The debate is left to the activists, in this case those in the pro-life and pro-choice camps. Neither group fully represents public opinion, though both claim to. What's so striking given the resources expended by both groups over the past quarter century is that neither group has moved public opinion.