This quite literally not a black or white issue. At it's core it's a question of what gives you a right to life and their are dozens of positions on that from self sustainability, being human, heartbeat, self awareness, and so forth.
There are only two positions that matter in the debate. In theory, you could come up with lots of wacky shit that no one cares about, I guess. In reality, the two positions that matter are either it's a baby, or it isn't. Any other position is irrelevant and likely to be nonsensical in its reasoning, and usually boils down to mental gymnastic variations on why it isn't a baby, i.e. "when it has a heartbeat, when it is conscious," etc. All of that crap comes across to me on the other side of the issue as the same position, namely the position that it isn't a baby.
It's literally not a baby for parts of the process. It goes from human gamete to human zygote to human fetus to human baby. There's not two definitive sides to this issue regardless of how strongly you feel about it. People are going to draw the line in different spots and most will do so in the middle not because of fence sitting, but because most people genuinely don't give a shit about zygotes and early fetuses.
This is demonstrably false or else we wouldn't be sitting here arguing about it. And I mean that not just in the sense of, us two retards on the Internet, but also in the sense of, a big public national debate over the issue due to Roe v Wade and yadda yadda. I can guarantee you that many pro-life people, probably the majority if I had to guess, believe that life begins at conception. Certainly every other pro life person I've spoken to does. People who do not believe life begins at conception do not describe themselves as pro-life in my experience. I have not met a single person who thinks that killing a 10 week old fetus is okay yet still describes themselves as "pro-life."
The two definitive sides are pretty much that: Either life begins at conception, or abortion is okay. Now, there might be some kind of internal debate on "your" side where you guys are trying to hash out exactly when it's okay to kill the baby, if it should be 15 weeks, or 25 weeks, or whatever. I suppose I wouldn't know, but I certainly don't seem to ever see that argued about. In this thread for example, it seems that little if any attention has been given to that question between different "pro choicers," whereas nearly all of the thread's attention is devoted to people who do not believe life begins at conception arguing with people like me who believe that it does.
And this mirrors my observation of the issue in society more broadly. This is why the left is able to get away with pushing for abortion until point of birth even though most of their own voters don't agree with that--because all of those people are forced to choose between that or people like me on the other side who want to ban it completely from point of conception. So, someone who still wants abortion to be available in the first trimester or something might decide that the left is the lesser of two evils there, creating the current all-or-nothing dichotomy in policy.