The trend of groups that oppose abortion is to move towards "humanizing" the fetus in a legal sense; i.e. giving it "individual" status in the eyes of the law. If that happens, then the circumstances of the conception would be irrelevant and all abortion would be necessarily illegal. A law that only allowed abortion for those who were raped or molested would seem to violate the equal protection concept for other women.
In a case where two beings occupy the same body space, and the interests of the two may be mutually exclusive (the woman wants an abortion, and presumably the fetus, if it could speak for itself, would want to not be aborted) then choices must be made. Who has greater standing? Whose needs/desires should win out? And since the needs of the baby do not end at birth, who would be obliged to care for a baby if a mother was forced to carry an unwanted pregnancy to term?
This is a link to a clinical description of the abortion process, rhetoric-free.
Since we are trying to keep this as emotion-free as possible, then I am merely suggesting some jumping off points for your debate. Anyone who wishes to debate abortion will do so to an empty keyboard on this side. Quoting Shay (I think) from another topic, I have no desire to "give CPR to the obviously dead horse."