If the sources behind Thomas Frank's 'What's the Matter with Kansas?' (2004) are to be believed, the abortion issue traces back even further into the 50s. IIRC from the book, abortion only became a wedge issue in the first place because of the GOP merge with trad Christianity in 50s Wichita.
I’ve read a lot of books on the topic and it seems that it really hit the ground running in the late 70s with the movement to elect Reagan. They needed a wedge issue to push evangelicals away from Jimmy Carter.
Totally fair! The overall point is absolutely valid and extremely frustrating. Watching the establishment Dems play games in days when the GOP plays games in decades is deeply defeating. Honestly, for the lot of us, it's just proof that the Dems don't care enough to put real effort in.