Here's a question: Why don't the pro-lifers join forces with the anti-Death Penalty folks to pass a Constitutional Amendment banning both these practices? Now I get the difference, but it would be a case of giving up something significant in order to gain a greater good. Of course, that would end the campaign cash, boots on the ground, etc. for the GOP from the "religious Right", so maybe this isn't a coming attraction.
Because neither one could pass on its own, so grouping them together would just make it go down in flames even worse. The soft pro-life supporters are largely pro-death penalty conservatives and vice versa. That and a constitutional amendment is a very unlikely way of moving any divisive social issue because it requires a supermajority.