A good summary of the danger, from Max Bergmann at DemocracyArsenal …

The big concern with a McCain presidency – a concern which I am surprised has not been vocalized more fully – is that the U.S. will lurch from crisis to crisis, confrontation to confrontation, whether it be with Iran, North Korea, Russia, Syria, Saudi Arabia, etc. The danger is that McCain’s pundit-like rhetoric will entrap the U.S. in descending spiral of foreign policy brinksmanship. Just think about the very likely scenario of McCain giving Iran/Russia a rhetorical ultimatum and Iran/Russia ignoring it. Now we are stuck – either we lose face by not following through on our threats or we follow through and go to war. We can’t afford such a reckless approach after the last eight years. For the next eight we need a president not a pundit.