The job of the Chief Executive of the United States is to represent the people. The President is responsible for doing what is in the best interest for the citizens of the United States using facts, advice, and evidence and not through his / her own personal religious beliefs. United States is the most religiously diverse country in the world, and it remains this way because its constitution has promised its citizens a freedom in which there is a separation between church and state. Since the President is the one person that represents all people in America, he / she should not be allowed to control our country based on his own faith and beliefs. The president's job is to make decisions that will speak for the majority of the people, no matter what race or religious background they may be. The President has an obligation to take the advice and information he gets from advisors and other high officials, and use that knowledge in order to plan what is best for the country as a whole, even if it conflicts with personal religious beliefs.
When religious beliefs are used to make policy decisions, one is imposing their religious belief upon others who might not agree, and ultimately is a violation of the first amendment that sets the separation of church and state. There is one exception in which the President may use his own personal beliefs. When there is no information leaning towards the right thing to do, or the pros and cons of a certain situation are balanced, the President should be able to use his own morals and personal belief to make a final decision. This is not something that should happen on a regular basis, but when there is no other sources leading one to the right direction, the only choice left is to use one's own morals, values, and beliefs to determine what direction might be best for the country as a whole.
The question on whether a President should be able to use his religious faith as a source to make policy decisions has recently become a debated issue with the Bush Faith Based Initiatives. A President, or any high official of the government, should not be able to use their religious beliefs in order to make policy decisions, except in the very unlikely occasion in which they have no other reliable source to base their decision.