A man sells Barack Obama car air fresheners in Charlotte, North Carolina (Photo by Scott Olson/Getty Images)

Every four years, Americans ask themselves: “Are you better off than you were before the presidential conventions?” To judge by the falling television ratings, the answer is not good.

This week in Charlotte, Barack Obama and his surrogates will be trying to fend off the Republican line that voters are worse off economically than when he took office. For most Americans, the answer is unfortunately “no” (median incomes have dropped almost five per cent since the recovery began in mid-2009).

The fault may lie more in the stars than with Mr Obama, who can plausibly argue that without his 2009 stimulus people would be far worse off. But his team will continue to respond with an unequivocal “yes” because in the game of politics if you admit any vulnerabilities then nobody – least of all the media – will let you change the subject. The formula is prebaked. Most voters feel worse off than they were four years ago. Yet Democrats are responding with a version of Groucho Marx’s: “Who do you believe? Me or your own lying eyes?” Little wonder the electorate is tuning out. Read more