Many people don't know what the word "pro-life" means politically. A Republican district leader in New York City told me she was pro-life, and then said but she believed women should have the choice. In other words, she wouldn't have an abortion herself, and that's what she thought "pro-life" meant. Who would say they were pro-death?
I believe this ignorance about the political meaning of "pro-life" is responsible for the 51% rating.
I think we are making progress but we're not at that point yet.