Barack Obama tried to shift the struggling US economy back to the centre of the presidential campaign on Friday after a Republican national convention dominated by the politics of character and culture.

The Democratic presidential nominee chided Republicans for glossing over the country’s economic difficulties and accused his opponent John McCain of offering nothing but more of the same failed policies of the past eight years. Both candidates returned to the campaign trail on Friday hoping to carry momentum from their party conventions into the final two-month sprint to the election, with most opinion polls showing Mr Obama narrowly ahead.