The most dangerous thing in politics is to blurt out what others are thinking but afraid to say. Geraldine Ferraro, the running mate of Walter Mondale in the doomed Democrat ticket of 1984, has just demonstrated this with pyrotechnic effect.

Asked to evaluate Hillary Clinton's chances, as a woman, of becoming president, Ferraro almost exploded with irritation: " I think whatever America feels about a woman becoming president takes a very secondary place to Obama's campaign, a kind of campaign that it would be hard for anyone to run against ... If Obama was a white man, he would not be in this position. He happens to be very lucky to be who he is. And the country is caught up in the concept."

At one level Ferraro's remark is just an unconscionable whine by a notable backer of Hillary Clinton. A good reason why Obama seems set to beat Mrs Clinton to the Democrat nomination is that he has the charm, oratorical gifts and physical presence which she notably lacks. To that extent, the colour of his skin has nothing whatever to do with her political problems.

At another level, Mrs Ferraro is absolutely right – and some black commentators have made a similar point without exciting anything like the same scandal or opprobrium. Shelby Steele, author of A Bound Man: Why We Are Excited About Obama And Why He Can't Win said recently on US television that: "Obama's campaign pretends to transcend race – but the paradox is that his campaign is all about race – and very little else."

Mrs Ferraro has been forced to resign from her official position as a Hillary Clinton fund-raiser, but the sky did not fall in on Shelby Steele. Of course, he was not so crass as to say that Obama is "very lucky"; but in essence Mr Steele has been making the same point. He argues that the unique attraction of Obama is that he is offering whites the emotionally seductive chance to vote for a black man who chooses never to raise the painful issue of race in a country divided by it. Steele, in fact, denigrates Obama for being "a bargainer rather than a challenger" in his dealings with white America. When Steele says Obama "can't win", he doesn't mean that he won't be elected president. He means that Obama won't change the politics of race in America.

Perhaps that has been the secret of Obama's cross-cultural appeal, but it is now being put under the most savage scrutiny by his desperate political opponents. In response to the Ferraro debacle, the Clintonites have turned their fire on Obama's pastor and religious mentor, the Rev Jeremiah Wright. It was one of Wright's sermons which supplied the title of Obama's book The Audacity of Hope. Inspired by Wright's electrifying oratory, Obama became an active member of the Rev Jeremiah's Trinity United Church of Christ. He and Michelle Obama were married in a ceremony conducted by Wright and his children were baptised by him – the Illinois senator and Jeremiah Wright have now been close friends for 20 years.

Yet Wright's church is essentially a black nationalist organisation. Its website's mission statement declares that "We constantly affirm our trust in God through cultural expression of a Black worship service". It goes on to proclaim its "allegiance to all Black leadership who espouse and embrace the Black Value System." These, says the Trinity United Church, are based on "Black Ethics", which must be "taught wherever Blacks are gathered."

Substitute the word "white" in place of "black" and you would have no trouble in identifying this as a racist church. Of course, we can all understand how such a peculiar form of sectarian Christianity has taken root in America; the idea of racial segregation was not invented by the slaves who form the genetic roots of today's African-Americans. It was not they who invented the notion of "one drop" racial identity – that if you had "just a drop of black blood" then you were black. (This form of identification is still potent, by the way. Genetically Obama is as white as he is black: politically, he could not escape identification as 'black', whatever he wanted to proclaim about himself.)

Now that Jeremiah Wright's sermons – including one proclaiming that "Jesus was a Black man oppressed by Whites" – are being funnelled en masse on to YouTube, Obama is hastily cutting himself loose from his religious mentor. Suddenly, Wright's very prominent endorsement has been removed from the "People of Faith'' section of the Obama campaign website.

Obama himself has just posted to the Huffington Post website that "The statements that Rev Wright made that are the cause of this controversy were not statements I personally heard him preach while I sat in the pews of Trinity." This, I'm afraid, has distinct echoes of Bill Clinton's "I smoked cannabis, but I didn't inhale."

There is, of course, another interpretation. A black friend of mine described the YouTube postings of Jeremiah Wright's sermons as Obama's "Willie Horton" moment – a reference to the images of a black rapist which were unscrupulously used by the Republicans to destroy Michael Dukakis' presidential campaign 20 years ago.

The same friend added, though, that there was no way that race could be kept out of this campaign, whatever anybody might wish. He pointed out that it is simply a fact that urban white working class voters in the Democratic primaries are overwhelmingly backing Hillary Clinton, while Obama has a symmetrically vast lead among black voters. Strictly on the policies of the two candidates, there is no logical reason why the electorate should vote along racial lines. This is something much more visceral.

As the New York Times pointed out yesterday: "Obama does best in areas that have either a large concentration of African-American voters or hardly any at all, but he struggles in places where the population is decidedly mixed. What this suggests, perhaps, is that living in close proximity to other races actually makes Americans less sanguine about racial harmony rather than more so."

Far from liberating America from the politics of race, as Obama's campaign purports to do, it seems quite likely that instead it will shed an uncomfortably penetrating light on the deep racial divisions that persist in a country still – and understandably – traumatised by the legacy of slavery.

Perhaps a President Obama could be the man to heal those wounds. The process of getting from here to there, however, will be a brutal business; and, as Geraldine Ferraro unwittingly demonstrated, it will reveal things about America that almost all of its politicians wish to keep hidden.

d.lawson@independent.co.uk