Religion and Politics? Help Me Understand.

I was discussing the election with my dad last night and I was kind of shocked when he said he wasn't voting this year. I can personally say that I never expected this as my dad is die hard voter when it comes to elections. I asked him why and he said one of the reasons was mainly based on Religion. He told me he wouldn't feel right voting for someone who was pro-choice. Now while McCain is pro-choice from what I read my dad just doesn't like him plain and simple. LoL. It made me think though. I know everyone talks about the seperation of church and state and things of that nature, but for someone who is very religious such as myself is it really possible to do such a thing? My father and I also differ on the issue of the Death Penalty. I for one am strongly opposed to it as my viewpoint more or less is they already have a life sentence so let them rot. I think killing them is sort of the easy way out and that they should have to sit in jail for the rest of their life and be reminded everyday about what they did. I also don't believe in taking a human life as punishment. Regardless of what you may think those murderers have families and people who love them too. I am just kind of lost as to how to make my decisions so that when it comes time for me to vote I will have a clear mind and know that I am voting for someone who shares my beliefs. Republicans it's mainly pro-life but mainly supporting the death penalty, democrats are mainly pro-choice and don't support the death penalty so it's like they say and excuse my language, but i'm dammed if I do and I'm dammed if I don't. If anyone has any advice please let me know. Thank you and God Bless!