At last week's Republican convention, to much bafflement and widespread derision, Clint Eastwood conducted a rambling interview with an invisible President Obama, as if he were sitting beside the actor in an empty prop chair. At the Democrats' gathering which opens today in Charlotte, North Carolina, the President will be there for real – and he needs to make a pretty good case for himself.
How easy it was four years ago. Back then, a young and luminous Candidate Obama seemed the man for the hour, generating a tide of enthusiasm that carried him to the White House. His victory was never really in doubt; he embodied hope and the promise of a new start. But the promise has not been translated into fact. Now he must persuade his jaded, uncertain country that he deserves a second term, despite presiding over the feeblest recovery from recession in three quarters of a century.
He can rightly lay a good deal of the blame on the Republicans who have blocked him at every turn in Congress and are far more responsible than Democrats for the partisan nastiness that has paralysed Washington. He will also accuse his opponents of being stuck in the past, offering "same-old" Reagan-era nostrums of tax cuts and deregulation – the trickle-down theorising that, as Mr Obama repeatedly says, "got us into this mess in the first place". But however justified the criticism, the President must do more.
Despite the disappointing economic recovery, he still has elements in his favour. Although his job approval ratings hover below the 50 per cent mark regarded as a minimum for re-election, Mr Obama remains personally popular, which suggests that Americans accept that he inherited an extraordinary crisis that was always going to take more than four years to resolve.
The vagueness of the so-called "five-point plan" that Mitt Romney outlined in Tampa is also an opportunity. Where his challenger set out mere aspirations, the President can be specific. Indeed, he must be specific. If he is to win a second term, Mr Obama has to spell out exactly what he would do with it.