The big driver for mass political involvement was the IRS yanking tax exemptions for segregated religious schools in 1976. That threw the religious right into high gear. They knew that openly endorsing segregation was a political liability so they went with abortion as the unifying issue instead.
Comments
https://www.patheos.com/blogs/slacktivist/2012/02/18/the-biblical-view-thats-younger-than-the-happy-meal/
https://www.politico.com/magazine/story/2014/05/religious-right-real-origins-107133
Being right had never been so bitter.
I often remark that if America became an evangelical theocracy, we’d have interdenominational wars the way they have tribal warfare in the Middle East.