It's true that politicians don't speak for Christians. It's also true (IMHO) that there is no such thing as a Christian politics. We are about preaching the Gospel and making ourselves better, more Christ-like, people. We are not about reforming the world by means of politics.
But! Christians can have political opinions and vote, just like any other citizen. I don't see a need for a separate forum section, unless it begins to dominate the main forum.