Perhaps the most important divide in the presidential campaign is between fact and fiction. There are, of course, other sharp distinctions based on region and religiosity, guns and gays, abstinence and abortion. But were the election to be decided on domestic concerns alone, George Bush would be near certain to join the ranks of one-term presidents - like his father after the aura of the Gulf war evaporated.

But one year after Bush's triumphant May Day landing on the deck of the USS Lincoln and appearance behind a "Mission Accomplished" sign, his splendid little war has entered a Stalingrad-like phase of urban siege and house-to-house combat. April has been the bloodiest month by far - 122 US soldiers killed compared with 73 last April in the supposed last month of the war. The unending war has inspired among Bush's backers a rally-round-the-flag effect, a redoubling of belief.

They believe in the cause as articulated by the vice president, Dick Cheney, this week in his speech at Westminster College in Fulton, Missouri, where Winston Churchill delivered his "iron curtain" oration. "You and I are living in such a time" of the "gravest of threats", said Cheney. Once again, he explained the motive for the Iraq war, implicitly conflating Saddam Hussein with al-Qaida and oblivious to the failure to discover WMD.

"His regime cultivated ties to terror," he said, "and had built, possessed and used weapons of mass destruction." And Saddam "would still be in power", he continued, coming to the point of his allegory, if John Kerry, cast as Neville Chamberlain to Bush's Churchill, had had his way.

These misperceptions are pillars of Bush's support, according to a study by the University of Maryland: 57 % of those surveyed "believe that before the war Iraq was providing substantial support to al-Qaida", and 45% "believe that evidence that Iraq was supporting al-Qaida has been found". Moreover, 65% believe that "experts" have confirmed that Iraq had WMD.

Among those who perceived experts as saying that Iraq had WMD, 72% said they would vote for Bush and 23% for Kerry. Among those who perceived experts as saying that Iraq had supported al-Qaida, 62% said they would vote for Bush and 36% for Kerry. The reason given by respondents for their views was that they had heard these claims from the Bush administration.

These political pulp fictions are believed out of faith and fear. This is a classic case study in "the will to believe", as the American philosopher William James called it. The greater insecurity would be not to believe Bush. It would mean the president had lied on issues of national security. And how could the Iraq war be seen as a pure, moral choice once good had been shown to be false? The idea of proof has shifted from fact to Fervor

The attack lines against Kerry are that he is an opponent of national security and un-American. When Kerry committed the gaffe of uttering the truth that many world leaders secretly hope for his victory, he provided the Bush campaign with an opening. The secretary of commerce, Donald Evans, has repeatedly said that Kerry "looks French". The Republican house majority leader, Tom DeLay, begins every speech: "As John Kerry would say, bonjour."

The European mission this month of Senator Joseph Biden, a Democrat on the foreign relations committee, is a telling if overlooked footnote to the campaign xenophobia. After meetings with Jacques Chirac and at Downing Street, he learned first-hand of the Bush administration's almost complete lack of consultation. Chirac offered first steps toward French assistance in Iraq, and Biden wrote a letter spelling them out to Bush, who referred him to the national security adviser, Condoleezza Rice, who in turn politely listened and never responded.

Meanwhile, the Republican chairman of the committee, Senator Richard Lugar, who has been granted just one meeting in the past year with the president, remarked to negligible press notice: "The diplomacy is deficient. By that I simply mean not many people agree with us, or like us, or are prepared to work with us. That will really have to change." A senate source told me: "The only hope for real internationalization is in regime change in the United States."

The brazen smears about Kerry's wounds and medals, his voting record on military programs as a senator, and his loyalty, have been communicated by the Bush-Cheney campaign through an estimated $50m in TV and radio advertising in less than 60 days in 17 swing states. This storm of unremitting negativity has bolstered the faith of his supporters, tested by recent events, and has managed to maintain the contest at a draw.

The attacks against Kerry are a bodyguard of lies to protect the original ones who are the praetorian guard of Bush's presidency.

· Sidney Blumenthal is former senior adviser to President Clinton and Washington bureau chief of Salon.com

© Guardian Newspapers Limited 2004

###