Let's assume that Republicans make a "step in the right direction" and outlaw abortion except in instances of rape, and maybe incest and/or risks to the life of the mother.
How does that play out, exactly? If any abortion is murder, how can there be exceptions? If it is against the law to perform or receive abortions, how do you provide for exceptions other than allowing abortion on demand?
Let's say I'm a 15 year old girl, and I attract the interest of a college basketball star. He takes me out on a date, plies me with alcohol, and brings me back to his apartment. I like him. I want to be his girlfriend. I'm drunk. Really drunk. We fool around. I let him feel me up, but when things start to get out of hand, I resist, but he doesn't take no for an answer. He overpowers me. I've been raped. I'm humiliated. I don't want to call my parents. He drives me home and acts as if everything is just fine. I go to my room and go to bed. There is nothing I can do. I can't prove anything. I'm too embarrassed and afraid to tell anyone, so I keep it to myself.
Five weeks later I discover I am pregnant. How the hell do I get an abortion? If I walk into Planned Parenthood and say "I've been raped, I want an abortion", and they grant it, is that not abortion on demand? Of course it is. Abortion on demand is the only viable solution to the rape exception, yet if you allow abortion on demand, there is no such thing as a rape exception.
If abortion is against the law except in cases of rape, the burden of proof must necessarily be on the victim. If it isn't, there is no actual restriction on abortion. Rapes are especially hard to prove, which is why most rapes are never even reported. What is the burden of proof required to qualify for the rape exception? If a burden of proof is required, then many, maybe most, maybe the overwhelming majority of rape victims would not be able to take advantage of the rape exemption. If a burden of proof is not required, then we are left with abortion on demand.
A rape exemption may sound reasonable, but it isn't. There simply isn't any way to implement it without discouraging rape victims from seeking abortion and humiliating those that do.