As an atheist I have to stab at this one: I avoid "God" when referring to my personal ideas about the universe. "God" only appears when I am talking about theists and their beliefs.

Others are not so cautious and use "God" as a shorthand for "whatever it is that is ultimately responsible for the universe, if anything."

One thing is sure--it is not possible to conclude that someone is a theist only because they refer to God. Even if they don't refer to "God" as I describe above, they may still just be a closeted atheist politician.