While there are many ways this is happening, there are two in particular that I'd like to mention and as I said they unknowingly play on the weaknesses already present in the church. The first is related to one of the Church's primary problems; it still acts like it is important. Not that it's not important in the lives of it's members and (for the churches still actively practicing real outreach) in the lives of those they help, because for them it is very important. Rather, it acts like it is important in the overall life of the culture. More specifically, it acts like it is central to community.
The truth is, it used to be. The Church used to be the center point of life in many towns and cities, not to mention families. However, a long time ago the culture moved forward as world dynamics shifted and the church planted it's roots and was passed by. Now (with some exceptions), the Church has gone from being central to being on the margins, way back where it planted it's roots – it just isn't central to culture anymore. Yet, it insist (demands?) on being treated as if it were. It seems to believe that it can just go about being what it once was and demand that those who participate do it our way, the “right way.” And people are staying away in droves.
When politicians play The God Card to garnish a few votes, they remind the rest of the US about one of the things they dislike about the Church, it's sense of privilege, entitlement and “rightness” - and they do it on a national platform.
Which brings me to the second way that politicians co-copting God is killing the church. If you are a Christian and you haven't read unChristian by David Kinnaman and Gabe Lyons let me highly recommend it (book review coming this week). I have to say, I am not a fan of some of the theology, but the research and what it reveals about the general public's perception of the church is both astonishing and right-on-the-money. One of the top issues it reveals is the Church's problem with being perceived as hypocritical. (Ok, you have to see where I'm going with this at this point).
Politicians are going to break their promises (I don't know why...that's just what they do. Get a history book and look it up). All these politicians flashing their particular brand of The God Card every time they have the platform ultimately just serves to remind people of the existing perception that the Church is hypocritical...and let's face it, we really don't need any help with that...just get a history book and look it up.