The headline could be “Majority backs abortion rights” *or* “Liberal pollster needs a competing headline.”
“Would you call yourself pro-choice or pro-life?”
versus
“Is abortion morally wrong?”
These are two different questions. Many who would say abortion is morally wrong would also say they are pro-choice. (This is the rather large “wrong for me but I can’t tell others what to do” category.)
What is legal is not always moral and what is moral is not always legal.
by 
If you can control the question you can determine the answer.
For example if you ask, ‘ Should it be the woman or the government who chooses if she is to have an abortion?’ It seems to me the answer would be the woman and thus a Pro Choice vote. However, if the Government in question is China’s and the question is asked; ‘Do you think that all should be done to ensure a mother can carry her baby to birth and oppose the government ?’, then I think a Pro Life answer will be seen. Pro Life answers would not be surprising with other questions. ‘Do you agree with the government’s financing and training of those who end the life of unborn or partially born babies?’ Or asking; ‘At what point in a baby’s development should it be ok to terminate the baby’s life?’.
Another thought: ‘Do we look to polls to tell us what is right?’
“Is abortion morally wrong?” is a rather over-simplistic question. I think it’d take more than one to get an accurate assessment of someone’s position on abortion.
I imagine the majority of people would consider it wrong in some circumstances but not in others – both pro-life and pro-choice. They would just disagree as to what those circumstances are. Then there are also people who believe that abortion is morally wrong, but not allowing abortion is even more wrong.