Hillary Clinton denied leaking the photo of Barack Obama wearing a turban, but her campaign manager says that even if she had, it would be no big deal. "Hillary Clinton has worn the traditional clothing of countries she has visited and had those photos published widely."

Sure she did. And George Bush put on a poncho in Santiago, while Paul Wolfowitz burned up YouTube with his anti-malarial African dance routines while World Bank president. The obvious difference is this: when white politicians go ethnic, they look funny; when a black presidential contender does it, he looks foreign - and when the ethnic apparel in question is vaguely reminiscent of the clothing worn by Iraqi and Afghan fighters (at least to many Fox viewers, who think any headdress other than a baseball cap is a declaration of war on America), the image is downright frightening.

The turban "scandal" is all part of what is being referred to as "the Muslim smear". It includes everything from exaggerated enunciations of Obama's middle name (Hussein) to the online whisper campaign that Obama attended a fundamentalist madrasa in Indonesia (a lie), was sworn in on a Qur'an (another lie), and if elected would attach speakers to the White House to broadcast the Muslim call to prayer (I made that one up).

So far Obama's campaign has responded with aggressive corrections that tout his Christian faith, attack the attackers and channel a cooperative witness before the House Un-American Activities Committee. "Barack has never been a Muslim or practised any other faith besides Christianity," states one fact sheet. "I'm not and never have been of the Muslim faith," Obama told a Christian News reporter.

Of course Obama must correct the record, but he doesn't have to stop there. What is disturbing about the campaign's response is that it leaves unchallenged the disgraceful and racist premise behind the entire "Muslim smear": that being Muslim is de facto a source of shame. Obama's supporters often say they are being "Swift-boated" (a pejorative term derived from the Swift Boat Veterans for Truth campaign against the 2004 presidential candidate John Kerry), casually accepting the idea that being accused of Muslimhood is tantamount to being accused of treason.

Substitute another faith or ethnicity, and you'd expect a very different response. Consider a report from the archives of the Nation. Thirteen years ago Daniel Singer, the magazine's late Europe correspondent, went to Poland to cover a presidential election. He reported that the race had descended into an ugly debate over whether one of the candidates, Aleksander Kwasniewski, was a closet Jew. The press claimed his mother was buried in a Jewish cemetery (she was still alive), and a popular TV show aired a skit featuring the Christian candidate dressed as a Hassidic Jew. "What perturbed me," Singer said, "was that Kwasniewski's lawyers threatened to sue for slander rather than press for an indictment under the law condemning racist propaganda".

We should expect no less of the Obama campaign. When asked during the Ohio debate about Louis Farrakhan's support for his candidacy, Obama did not hesitate to call Farrakhan's antisemitic comments "unacceptable and reprehensible". When the turban photo flap came up in the same debate, he used the occasion to say nothing at all.

Farrakhan's infamous comments about Jews took place 24 years ago. The orgy of hate that is the "Muslim smear" is unfolding in real time, and it promises to greatly intensify in a general election. These attacks do not simply "smear Barack's Christian faith", as John Kerry claimed in a campaign mailing. They are an attack on all Muslims, some of whom actually do exercise their rights to cover their heads and send their kids to religious school. Thousands even have the very common name Hussein. All are watching their culture used as a crude bludgeon against Obama, while the candidate who is the symbol of racial harmony fails to defend them - this at a time when US Muslims are bearing the brunt of the Bush administration's assaults on civil liberties, including dragnet wiretapping, and are facing a documented spike in hate crimes.

Occasionally, though not nearly enough, Obama says that Muslims are "deserving of respect and dignity". What he has never done is what Singer called for in Poland: denounce the attacks themselves as racist propaganda, in this case against Muslims.

The core of Obama's candidacy is that he alone - having lived in Indonesia as a boy and with an African grandmother - can "repair the world" after the Bush wrecking ball. That repair job begins with the 1.4 billion Muslims around the world, many convinced that the US has been waging a war against their faith. This perception is based on facts, among them the fact that Muslim civilians are not counted among the dead in Iraq and Afghanistan; that Islam has been desecrated in US-run prisons; and that voting for an Islamist party resulted in collective punishment in Gaza. It is also fuelled by the rise of a virulent strain of Islamophobia in Europe and North America.

As the most visible target of this rising racism, Obama has the power to be more than its victim. He can use the attacks to begin the very process of global repair that is the most seductive promise of his campaign. The next time he's asked about his alleged Muslimness, Obama can respond not just by clarifying the facts but by turning the tables. He can state that while a liaison with a pharmaceutical lobbyist may be worthy of scandalised exposure, being a Muslim is not. Changing the terms of the debate this way is not only morally just but tactically smart - it's the one response that could defuse these hateful attacks. The best part is this: unlike ending the Iraq war and closing Guantánamo, standing up to Islamophobia doesn't need to wait until after the election. Obama can use his campaign to start now. Let the repairing begin.

A version of this article appears in the Nation (thenation.com) naomiklein.org