If you are interested in this subject, I encourage you to read the book GOD IN THE WHITE HOUSE by Randall Balmer (2007), which examines how politics and religion have interacted from the time of John F. Kennedy to George W. Bush. Amazon.com and Half.com both carry it at a discount.
The paper below was originally titled "God in the White House." The title has been changed and the content slightly updated for this post. It was my first graduate paper and was written in 2003, when George W. Bush was still in the White House.