Everything you said was in place before 1980, too? Why did we not see this phenomenon then?
Valid question and I don't have a good answer. My best guess would be that women as a group were not very involved in politics prior to the '70's. After Roe v. Wade and the organization of NOW, the issues became more polarized and the liberals got organized first. They tend to vote in blocks more than conservatives do....that's my initial take on your question. I would be glad to hear more if you have a different opinion.