That distinguishes abortion from other contentious social issues, such as same-sex marriage and marijuana legalization, where overall public opinion — led by the young — has shifted dramatically in favor of a more liberal position.
For decades, polls have shown that most people want abortion to be available to women, at least in the early stages of pregnancy, when the vast majority occur.
But Americans get increasingly uncomfortable with the procedure as a fetus gets closer to viability. In December, a Gallup poll found roughly six in 10 saying abortion should be legal in the first three months of pregnancy, but support dropped to 27 percent in the second trimester and to 14 percent in the third.
Data just released by the National Opinion Research Center show that most Americans think the woman's decision to have an abortion is justified in some instances — rape (where 78 percent support abortion as an option), fetal deformity (77 percent) and serious danger to her health (87 percent), for example. But they do not support it when an abortion is sought because the woman believes she is too poor to have more children (a situation in which 45 percent say they approve of an abortion) or doesn't want to marry the father (42 percent).
The fact that there are so many facets to when and why a woman may seek an abortion means the political argument around it — even more than most issues — is likely to be won by the side that more agilely frames the question.
If the focus is on the woman, abortion rights advocates have found they can usually gain the upper hand.
"The more you have people think about woman's personal decision-making — how you can't have someone else make that decision, especially politicians" — the better it goes for those who support abortion rights, said Democratic pollster Celinda Lake.