He made a speech in which he flat out opposes any war with Iran. Take a listen:
I disagree with some of his characterizations of the Iranian regime (he uses necon framing and rhetoric to make Iran seem far more of a threat to Israel and the US than it actually is), but at least he makes it clear that another war in the Middle East is an option we need to take off the Bush banquet table. Note that when he said Bush is not authorized to go to war with Iran was also when he got his loudest applause from his audience (good folks in Clinton, Iowa, by the way). Something of which other candidates should take note. Democrats and Independents don’t want another war with Iran. When you speak out against the Bush push for military action against Iran, you gain credibility as a potential President, and a candidate for whom people will want to cast their vote, both in the primaries and in the general election.