Andrew Sullivan has been running a series of his reader's anecdotes on abortion following the murder of Dr. George Tiller Sunday. Go here for a search list of the articles. They're all well worth reading. This lady, forced to have a late-term abortion because of a genetic defect in her baby, makes possibly the best point:
"I think I speak for a lot of people when I say that I have concluded that a decision to undergo abortion or continue a pregnancy is often made instinctively, with a nearly primal conviction that it is the right thing to do under the circumstances. Trying to impose a rigid moral framework based on an extreme notion of equality of personhood doesn't even begin to speak to the complexities of what most people experience when trying to decide this question for themselves."