The invaluable Paul Krugman (via Common Dreams) explains here why Bush cannot be trusted to do the right thing with Iran, any more than he could be trusted in Iraq. Key quote:
Why might Mr. Bush want another war? For one thing, Mr. Bush, whose presidency is increasingly defined by the quagmire in Iraq, may believe that he can redeem himself with a new Mission Accomplished moment.
And it's not just Mr. Bush's legacy that's at risk. Current polls suggest that the Democrats could take one or both houses of Congress this November, acquiring the ability to launch investigations backed by subpoena power. This could blow the lid off multiple Bush administration scandals. Political analysts openly suggest that an attack on Iran offers Mr. Bush a way to head off this danger, that an appropriately timed military strike could change the domestic political dynamics.
Does this sound far-fetched? It shouldn't. Given the combination of recklessness and dishonesty Mr. Bush displayed in launching the Iraq war, why should we assume that he wouldn't do it again?
Yes, Bush would launch a war timed to help Republican election prospects. There is no level of political venality to which he will not sink. Krugman warns us that we've got to get over the idea that Bush "wouldn't do such a thing". On the contrary, he has shown himself capable of anything. That's what makes him the most dangerous president in American history.