Anyway Obama has probably got this one nailed. Hard to compete with this argument from Greenwald.
But if there is one thing the 2008 campaign should have permanently taught, it is that campaign rhetoric often bears little relationship to what a person will do once empowered. More important, it is almost certainly the case that an Obama-led attack on Iran would generate far more public support than a Romney-led attack, because most Democrats will almost certainly cheer for the former while pretending to be horrified by the latter, will while Republicans would support both (that's the dynamic that made the very same "counter-terrorism" policies that were so divisive in the Bush years become wildly popular once Obama embraced them).
That's true on the international level as well. Recall the 2008 CIA report fretting about growing anti-war sentiment in western Europe and concluding that the best weapon to safeguard against its continuation would be the election of Obama. That's because, the CIA presciently realized, Obama's election would massively increase public support for US wars because it would be a kind, sophisticated, progressive constitutional scholar rather than a swaggering, evangelical Texas cowboy who would be the face of them. Add to all that the Nixon-to-China dynamic - just as only a conservative president could have established relations with the Chinese Communists, arguably only a Democratic president could start a new war in the Muslim world, cut Social Security, etc. - and the picture is far more muddled than many like to depict it as being.