There is no such thing and selling your soul to the devil because you dislike Santorum and Catholics at a discount seems kind of foolhardy.
There is an "establishment clause" and a "free exercise clause". To exercise means to do vigorously and the notion that religion is barred from influencing debate in government in the public square is a left wing secular nut philosophy.
In fact I just had to explain this to a liberal at Politico and the fact that I now have to explain it to a self identified conservative here at FR makes me throw up as well.