This should come down to a simple couple step logical discussion without any politics or religion involved.
1. Do human lives/life have intrinsic value/rights? The logical answer, according to all our laws, is yes (you can't murder someone you don't like).
2. If human life has intrinsic value and rights, when does human life begin and who should determine when that timeframe is?
3. I think its safe to say that most would agree that academic biologists should be determining when human life begins right? Not religions (Christians/Jews/Muslims), not politicians (Ds or Rs).
4. Once that life is determined to "begin" it deserves the same Constitutional protections as everyone else has, like say a 5 year old we all agree is protected from harm.
5. With all that being said...
95% of biologists say life begins at conception.
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3211703