He has been making that promise to any right wing evangelical that will listen on the campaign trail. In fact, his current SCOTUS pick will likely help him reach that goal. The evangelicals have had enough of losing power and influence thank you very much. Rather than re-examine their policies, they decided long ago that it's the evil gubbmint keeping them so oppressed as they are. The interesting part is, I think it's been the wall that has retained much of religion's power and influence in this country. They have much weaker protections in Europe, and look at how religion is doing over there. What is also interesting is all the polls showing religion losing it's power, prestige and followers. Some of the most often cited reasons for people losing their religious outlook on life is the intermingling of religion and politics, and evangelical's beliefs about homosexuality.
I have a sneaky suspicion that were the Johnson amendment repealed, they'll be trading some short term gain for a steep fall off instead of a long, slow decline. If I were evangelical, I would try to remember that the wall of separation of powers doesn't just protect government from religion, but religion from government. Look at how Trump is already threatening removing government funding for things he doesn't like. Shall the government be able to remove funding for religious practices that it views unfavorably as well?
Ironically, religion was never very good at the long view of things.
