There are those who argue that the pledge is constitutional because it is not a prayer.  Such a notion is a fallacy.  It would presuppose that the only thing that could be classified as religious is prayer making, which is clearly not the case.  The notion of a "nation under God" is a declaration and affirmation of a specific deity and religious ideology, and thus both an acknowledgment and an oath of fealty to an entity of a strictly religious kind.  It does not matter that it is claimed to be an expression of some kind of "civil religion" either, as it still amounts to government endorsement of a specific religious ideology and furthermore one that is prejudiced in its monotheistic emphasis.