Last I checked the people who identify as "pro-choice" is dropping and the people who identify as "pro-life" is rising because they have become loaded words. The anti-abortion crowd have created an incorrect association between the label "Pro-choice" and baby killing.
However when the poll is worded to be should women be free to be allowed the choice to have an abortion versus that choice being taken away by making abortion illegal, the population in general is overwhelmingly supportive of the pro-choice position, in the tune of 70%
Basically everyone actually is for life and want life to be as good as possible for as many as possible. With this comes the belief that we should be free to make our own choices and not have them controlled by the government. Unfortunately the Pro-life movement has chosen to twist the words and create a false dichotomy in their favor.