US presidential elections rarely turn on foreign policy. This one less than most. When Mitt Romney spoke to the Republican convention, he made no mention of the young Americans fighting and dying in the nation’s longest war. At the Democratic party convention Barack Obama gave Afghanistan a glancing reference – but only to underline that he would soon be bringing the troops home.

On the campaign trail, the world struggles to gain a mention. Mr Romney offered Republican delegates a brief, boilerplate criticism of the president as soft on adversaries and neglectful of allies, particularly Israel. Mr Obama, in an only slightly fuller account of abroad, claimed credit for the reassertion of US power in the Pacific and for the death of Osama bin Laden.

The killing this week of American diplomats in Benghazi and spreading violence against US embassies in the Middle East in response to a film mocking Islam have put the world back on the front pages. The US cannot escape the consequences of its unrivalled global reach. The real election battlegrounds, though, are the economy and the plight of the middle classes.