Barack Obama insisted yesterday he was the man to guide the US economy back to health as he prepared for one of the biggest moments of his political career: laying out his vision for a second term at the Democratic national convention.

At a rally in the swing state of Ohio, the president co-opted Mitt Romney’s weekend claim that the economy needed “a new coach” to attack his Republican rival’s plans with sporting metaphors. “I’ve got some additional advice on the Romney-Ryan game plan. Punt it away,” Mr Obama told a crowd of car workers in Toledo, Ohio. “It won't work. It won't win the game.”

No Republican has won an election without winning Ohio and Mr Obama attacked his rival in an effort to ensure Mr Romney continued that run. “You don't need that coach. That’s a losing season,” he said.