The moral and social questions behind these two issues are completely different.
The ability to access an abortion is based on the idea that every woman has the right to decide whether she wants to (or is able to) carry a pregnancy to term, and whether she feels ready to take responsibility for a child and guide it through life. Proponents of abortion rights know that safe and legal abortion is life-saving for women. Without it, large numbers of women resort to unsafe abortion and risk serious injury or death. Women also cannot control their own lives when their plans and dreams are contingent on whether or not they get pregnant accidentally.
Fetuses are not persons under the law, nor are they sentient individuals who are part of society. An unwanted fetus is also not “innocent” in the sense that it is co-opting a woman’s body against her will and imposing physical and mental health risks upon her.
In contrast, victims of the death penalty are mature and conscious beings who are being punished for a serious crime, usually murder. Most liberal people are against the death penalty because they feel it is inhumane, discriminates against minorities, does not deter violent crime, and carries too great a risk of killing innocent people who were wrongfully convicted.
Therefore, support for both abortion rights and abolishing the death penalty is rooted in justice, human dignity, and respect for life. Virtually all developed countries and many developing countries have abolished the death penalty. But U.S. states with the most anti-choice restrictions also tend to support the death penalty. They are not so much “pro-life” as against “sin”, and are therefore pro-punishment.
American Civil Liberties Union, The Case Against the Death Penalty (2012)
Anne Nicol Gaylor, Women’s Medical Fund, “Abortion Is a Blessing” (1975)
Joyce Arthur, Pro-Choice Action Network, “The Fetus Focus Fallacy” (2005)
Will Saletan, Slate: Why Pro-Lifers Kill