Yeah, this is the answer right here. There was always a latent effect on politics - i.e. since American is so heavily Protestant, Kennedy getting elected as a Catholic was kind of a big deal, but that was more of a passive preference and not so blatantly driven by party strategy. And that effects all countries, whether you want to believe it or not - America's not alone here by any means.

But, I remember when Reagan and the 'Moral Majority' (which was neither moral, nor the majority) kicked off and turbocharged the whole thing, and that's when fundamentalists started pushing congregations on their voting patterns in an organized way. It was like someone flipped a switch and the message was coordinated across the country.