You are correct but that does not change the fact that abortion is, in most cases, morally indefensible.
I am sure public opinion did not support revolution against England or the abolition of slavery but somehow we got those two things behind us.
So, the religious right can stay in the party and get a portion of their agenda, or it can stay home and get nothing, or it can start a third party and get nothing, or it can go DemocRAT and get nothing.