There is no separation of church & state in the US Constitution. There is however the establishment clause which states that the government does not have the power to establish an official state religion. This gets confused a lot so people often invoke a constitutional separation of church & state that does not and has not ever existed.
However, with regards to stem cell research, Bush dropped the ball. Part of seeking "the good life" for most people includes advances in technology that can potentially make their lives, or the lives of loved ones better. The veto pretty much flies in the face of popular opinion, on an issue that is non-partisan. It's sad, for the people that have MS, MD, Alzheimer's, and numerous other diseases and illnesses that could have benefitted from the bill's passage.
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