“Bush has said that we will not allow Iran to obtain nuclear weapons. Is that just an empty threat? The Iranians seem to think so”
That would be a big mistake for the Iranians to think so, credibility or not. Bush has shown that he follows thru on his word, public opinion be damned!
Bush doesn't have that kind of power to initiate a war with Iran without consulting Congress or the American people. We went into Iraq after getting a UN resolution and a joint resolution from Congress approving the action.
Bush has not always kept his word, e.g., CFR, not granting amnesty to illegals, etc.