First it looked as though the central issue of the US presidential election would be Iraq. Then it seemed the economy was the story. Now, six weeks before the election, another debate dominates the presidential race. It involves Vietnam but is not the Vietnam debate most political strategists predicted.

Recall the expectations of leading Democrats in the run-up to this election year. Everyone remembered the success of John McCain in 2000, including his unexpected popularity among Democrats. The McCain example made another hero - John Kerry, with his silver and bronze stars and three purple hearts - seem especially attractive. Democratic leaders were, however, also convinced that anti-war activists could be winners as well. After all, most senior Democrats - and the majority of journalists who cover them - long believed that the Vietnam war was a mistake. Here again, Mr Kerry, a prophet of the anti-Vietnam war movement, fitted the bill. The tape of a highly believable young Mr Kerry's interview with Dick Cavett, the television host, and his 1971 protest testimony about "winter soldiers" -were both regarded as pluses. Three decades ago Mr Kerry told Congress that the idealistic side of the battle was pointless, that in Vietnam "we found most people didn't even know the difference between communism and democracy". Mr Kerry also spoke about how other veterans had told him of mass war crimes by US soldiers.