Abortion rights and their effect on the election

In a very telling moment, I was watching Larry King last night and even Ben Stein (a staunch Republican) agreed that McCain won't be able to fix the economy and pretty much agreed with the Democratic strategist and Obama's positions. When the Democrat asked him why he didn't come over to Obama, he said "because he doesn't support my views on abortion".

Now I understand abortion is a touchy subject for a lot of people, but is that the only issue some people vote on anymore? The thing about abortion, in my mind (and I am sure this wouldn't mesh with some folks, especially my fellow Catholics, but hear me out), is that it is a religious issue. Why you may ask? Well, because there has been no definitive scientific study that pinpoints exactly when life begins (even the definition of life is disputed). So when you are against abortion, for the majority of people I would guess, you are against it on religious grounds. Now last time I checked, our Constitution states that "Congress shall make no law respecting an establishment of religion". This is my whole point. If we disparage the Taliban and other middle eastern countries for trying to establish a theocracy based on Islam, why is it OK to make laws based on religion here? We are supposed to be a secular nation, with a separation of church and state. I might not agree with abortion because of my faith, but does that give me the right to force that view upon another who might not share my religious views?

To be honest though, this is an issue I've always struggled with. I guess it's hard to decide where that line is when government should be involved in your personal life. I'm mainly throwing this out there because I'd like to hear the opinions of others. I've always known where I've stood on abortion personally (which I guess is easier if you are a guy), but I've had trouble reconciling that with what its place in America should be.