Reread and looked at the structure.
I am now unsure exactly what the writer had in mind. As most of the MSM would have, in their typically bad usage, meant any number of things. As this is National Review, I usually give them the benefit of the doubt. I do tend to think that the participle dangles a bit.
I agree you can definitely read it both ways. But, given the author’s perspective in the article, I concluded he is not saying the president is a Christian.