Party realignment in the United States
Many "values voters" became Republicans.  These were people who voted based on their own form of morality. To them, abortion and gay rights were immoral. In the 1960s, sex was closely tied to morality.  In this way, people who opposed abortion and gay rights, for example Jerry Falwell, and the changes to society happening in the 1960s and 70s, became Republicans. (No source cited, dubious credibility.)