The results of a recent Zogby poll on abortion are available online here. It was a large poll with 30,117 respondents and has a low margin of error of +/- 0.6 percentage points.
Things that I find interesting include:
Individuals who said they would support a Democrat congressional candidate were much more likely to answer "not sure" when asked about a specific policy/law than individuals who'd favor a Republican congressional candidate.
17% of individuals who'd support of Democrat for Congress in 2006 said "not sure" when asked "Do you agree or disagree that abortion ends a human life?"
20% of Democrat supporters and 17% of independent said "not sure" when asked, "Which of the following best describes when you think life begins?"
35% of individuals who'd support a Democrat for Congress in 2006 said they think life begins at birth.