In this most unconventional of US elections, now overshadowed by a financial crisis for the ages, an ancient truism of presidential politics is being overturned. John McCain is finding out that negative campaigning, a guaranteed winner for Republicans in elections past, is simply not working as it should in 2008.
Over the past few days, the Republicans have stepped up their efforts to portray Barack Obama as some kind of hostile alien in America's midst. Mr McCain's running-mate, Sarah Palin, accuses the Democrat of "palling around with terrorists", while Republican campaign events now question Mr Obama's policies less than his patriotism, honesty and basic fitness as a human being. In a sense, you can't blame them. The economic crisis has transformed the election, pushing national security concerns like Iraq and the genuine terrorist threat out of the headlines.
Mr McCain's greatest strength has thus been rendered all but useless. Voters are fixated on the issues of jobs, wages and savings, where Democrats always have a large, in-built advantage. Nor does it help that Mr McCain, who by his own admission is no economic expert, visibly flails for answers, changing his policies daily with no sign that he is in touch with the desperate anxieties of voters.
Faced with such difficulties, the Republicans have understandably tried to change the subject, as they did to devastating effect against Michael Dukakis in 1988 and John Kerry in 2004. In similar circumstances, the black arts of politics would probably work today. An image would be sealed of Mr Obama as callow, shady, unpatriotic and somehow "different" – in other words black. This time, however, such character assassination comes across as petty and irrelevant compared to the real problems facing not just America, but individual citizens.
Despite his current lead, an Obama victory is not certain. In 1980, it was only in the final days of the campaign that the tide turned irrevocably against Jimmy Carter, as voters found themselves comfortable with the challenger Ronald Regan. An equivalent moment in 2008 has not yet arrived. But if Mr McCain is to win, it will not be by slinging mud.