It all comes down to the fact that there was no "right" to abortion until the Supreme Court smoked some Angel Dust laden weed and pulled it from their hooka.
No reason to worry about what's actually written in the U.S. Constitution when a good halucination will do the trick.
As far as the idea that there are fewer Democrats because of abortion, as long as killing another human being is easier to face than taking responsibility for your actions, there will always be abortion.