History, I suspect, will look back on the past six months as an example of America going through one of its collectively deranged episodes - rather like Prohibition from 1920-33, or McCarthyism some 30 years later. This time it is gloating, unshackled sexism of the ugliest kind. It has been shamelessly peddled by the US media, which - sooner rather than later, I fear - will have to account for their sins. The chief victim has been Senator Hillary Clinton, but the ramifications could be hugely harmful for America and the world.

I am no particular fan of Clinton. Nor, I think, would friends and colleagues accuse me of being racist. But it is quite inconceivable that any leading male presidential candidate would be treated with such hatred and scorn as Clinton has been. What other senator and serious White House contender would be likened by National Public Radio's political editor, Ken Rudin, to the demoniac, knife-wielding stalker played by Glenn Close in Fatal Attraction? Or described as "a fucking whore" by Randi Rhodes, one of the foremost personalities of the supposedly liberal Air America? Could anybody have envisaged that a website set up specifically to oppose any other candidate would be called Citizens United Not Timid? (We do not need an acronym for that.)

I will come to the reasons why I fear such unabashed misogyny in the US media could lead, ironically, to dreadful racial unrest. "All men are created equal," Thomas Jefferson famously proclaimed in 1776. That equality, though, was not extended to women, who did not even get the vote until 1920, two years after (some) British women. The US still has less gender equality in politics than Britain, too. Just 16 of America's 100 US senators are women and the ratio in the House (71 out of 435) is much the same. It is nonetheless pointless to argue whether sexism or racism is the greater evil: America has a peculiarly wicked record of racist subjugation, which has resulted in its racism being driven deep underground. It festers there, ready to explode again in some unpredictable way.

To compensate meantime, I suspect, sexism has been allowed to take its place as a form of discrimination that is now openly acceptable. "How do we beat the bitch?" a woman asked Senator John McCain, this year's Republican presidential nominee, at a Republican rally last November. To his shame, McCain did not rebuke the questioner but joined in the laughter. Had his supporter asked "How do we beat the nigger?" and McCain reacted in the same way, however, his presidential hopes would deservedly have gone up in smoke. "Iron my shirt," is considered amusing heckling of Clinton. "Shine my shoes," rightly, would be hideously unacceptable if yelled at Obama.

Evidence to the contrary notwithstanding, American men like to delude themselves that they are the most macho in the world. It is simply unthinkable, therefore, for most of them to face the prospect of having a woman as their leader. The massed ranks of male pundits gleefully pronounced that Clinton had lost the battle with Obama immediately after the North Carolina and Indiana primaries, despite past precedents that strong second-place candidates (like Ronald Reagan in his first, ultimately unsuccessful campaign in 1976; like Ted Kennedy, Gary Hart, Jesse Jackson and Jerry Brown) continue their campaigns until the end of the primary season and, in most cases, all the way to the party convention.

None of these male candidates had a premature political obituary written in the way that Hillary Clinton's has been, or was subjected to such righteous outrage over refusing to quiesce and withdraw obediently from what, in this case, has always been a knife-edge race. Nor was any of them anything like as close to his rivals as Clinton now is to Obama.

The media, of course, are just reflecting America's would-be macho culture. I cannot think of any television network or major newspaper that is not guilty of blatant sexism - the British media, naturally, reflexively follow their American counterparts - but probably the worst offender is the NBC/MSNBC network, which has what one prominent Clinton activist describes as "its nightly horror shows". Tim Russert, the network's chief political sage, was dancing on Clinton's political grave before the votes in North Carolina and Indiana had even been fully counted - let alone those of the six contests to come, the undeclared super-delegates, or the disputed states of Florida and Michigan.

The unashamed sexism of this giant network alone is stupendous. Its superstar commentator Chris Matthews referred to Clinton as a "she-devil". His colleague Tucker Carlson casually observed that Clinton "feels castrating, overbearing and scary . . . When she comes on television, I involuntarily cross my legs." This and similar abuse, I need hardly point out, says far more about the men involved than their target.

Knives out

But never before have the US media taken it upon themselves to proclaim the victor before the primary contests are over or the choice of all the super-delegates is known, and the result was that the media's tidal wave of sexism became self-fulfilling: Americans like to back winners, and polls immediately showed dramatic surges of support for Obama. A few brave souls had foreseen the merciless media campaign: "The press will savage her no matter what," predicted the Washington Post's national political correspondent, Dana Milbank, last December. "They really have their knives out for her, there's no question about it."

Polling organisations such as Gallup told us months ago that Americans will more readily accept a black male president than a female one, and a more recent CNN/Essence magazine/ Opinion Research poll found last month that 76 per cent think America is ready for a black man as president, but only 63 per cent believe the same of a woman.

"The image of charismatic leadership at the top has been and continues to be a man," says Ruth Mandel of Rutgers University. "We don't have an image, we don't have a historical memory of a woman who has achieved that feat."

Studies here have repeatedly shown that women are seen as ambitious and capable, or likeable - but rarely both. "Gender stereotypes trump race stereotypes in every social science test," says Alice Eagley, a psychology professor at Northwestern University. A distinguished academic undertaking a major study of coverage of the 2008 election, Professor Marion Just of Wellesley College - one of the "seven sisters" colleges founded because women were barred from the Ivy Leagues and which, coincidentally, Hillary Clinton herself attended - tells me that what is most striking to her is that the most repeated description of Senator Clinton is "cool and calculating".

This, she says, would never be said of a male candidate - because any politician making a serious bid for the White House has, by definition, to be cool and calculating. Hillary Clinton, a successful senator for New York who was re-elected for a second term by a wide margin in 2006 - and who has been a political activist since she campaigned against the Vietnam War and served as a lawyer on the congressional staff seeking to impeach President Nixon - has been treated throughout the 2008 campaign as a mere appendage of her husband, never as a heavyweight politician whose career trajectory (as an accomplished lawyer and professional advocate for equality among children, for example) is markedly more impressive than those of the typical middle-aged male senator.

Rarely is she depicted as an intellectually formidable politician in her own right (is that what terrifies oafs like Matthews and Carlson?). Rather, she is the junior member of "Billary", the derisive nickname coined by the media for herself and her husband. Obama's opponent is thus not one of the two US senators for New York, but some amorphous creature called "the Clintons", an aphorism that stands for amorality and sleaze. Open season has been declared on Bill Clinton, who is now reviled by the media every bit as much as Nixon ever was.

Here we come to the crunch. Hillary Clinton (along with her husband) is being universally depicted as a loathsome racist and negative campaigner, not so much because of anything she has said or done, but because the overwhelmingly pro-Obama media - consciously or unconsciously - are following the agenda of Senator Barack Obama and his chief strategist, David Axelrod, to tear to pieces the first serious female US presidential candidate in history.

"What's particularly saddening," says Paul Krugman, professor of economics and international affairs at Princeton and a rare dissenting voice from the left as a columnist in the New York Times, "is the way many Obama supporters seem happy with the . . . way pundits and some news organisations treat any action or statement by the Clintons, no matter how innocuous, as proof of evil intent." Despite widespread reporting to the contrary, Krugman believes that most of the "venom" in the campaign "is coming from supporters of Obama".

But Obama himself prepared the ground by making the first gratuitous personal attack of the campaign during the televised Congressional Black Caucus Institute debate in South Carolina on 21 January, although virtually every follower of the media coverage now assumes that it was Clinton who started the negative attacks. Following routine political sniping from her about supposedly admiring comments Obama had made about Ronald Reagan, Obama suddenly turned on Clinton and stared intimidatingly at her. "While I was working in the streets," he scolded her, ". . . you were a corporate lawyer sitting on the board of Wal-Mart." Then, cleverly linking her inextricably in the public consciousness with her husband, he added: "I can't tell who I'm running against sometimes."

One of his female staff then distributed a confidential memo to carefully selected journalists which alleged that a vaguely clumsy comment Hillary Clinton had made about Martin Luther King ("Dr King's dream began to be realised when President Lyndon Johnson passed the Civil Rights Act of 1964") and a reference her husband had made in passing to Nelson Mandela ("I've been blessed in my life to know some of the greatest figures of the last hundred years . . . but if I had to pick one person whom I know would never blink, who would never turn back, who would make great decisions . . . I would pick Hillary") were deliberate racial taunts.

Another female staffer, Candice Tolliver - whose job it is to promote Obama to African Americans - then weighed in publicly, claiming that "a cross-section of voters are alarmed at the tenor of some of these statements" and saying: "Folks are beginning to wonder: Is this an isolated situation, or is there something bigger behind all of this?" That was game, set and match: the Clintons were racists, an impression sealed when Bill Clinton later compared Obama's victory in South Carolina to those of Jesse Jackson in 1984 and 1988 (even though Jackson himself, an Obama supporter, subsequently declared Clinton's remarks to be entirely inoffensive).

The pincer movement, in fact, could have come straight from a textbook on how to wreck a woman's presi dential election campaign: smear her whole persona first, and then link her with her angry, red-faced husband. The public Obama, characteristically, pronounced himself "unhappy" with the vilification carried out so methodically by his staff, but it worked like magic: Hillary Clinton's approval ratings among African Americans plummeted from above 80 per cent to barely 7 per cent in a matter of days, and have hovered there since.

I suspect that, as a result, she will never be able entirely to shake off the "racist" tag. "African-American super-delegates [who are supporting Clinton] are being targeted, harassed and threatened," says one of them, Representative Emanuel Cleaver. "This is the politics of the 1950s." Obama and Axelrod have achieved their objectives: to belittle Hillary Clinton and to manoeuvre the ever-pliant media into depicting every political criticism she makes against Obama as racist in intent.

The danger is that, in their headlong rush to stop the first major female candidate (aka "Hildebeast" and "Hitlery") from becoming president, the punditocracy may have landed the Democrats with perhaps the least qualified presidential nominee ever. But that creeping realisation has probably come too late, and many of the Democratic super-delegates now fear there would be widespread outrage and increased racial tension if they thwart the first biracial presidential hopeful in US history.

But will Obama live up to the hype? That, I fear, may not happen: he is a deeply flawed candidate. Rampant sexism may have triumphed only to make way for racism to rear its gruesome head in America yet again. By election day on 4 November, I suspect, the US media and their would-be-macho commentators may have a lot of soul-searching to do.

In this comment piece on sexist language in the US media in relation to Hillary Clinton Andrew Stephen suggested that Carl Bernstein had publicly declared his disgust for Hillary Clinton's thick ankles. We are informed that Carl Bernstein intended, in his biography of Hillary Clinton, to refer to comments made by others about her when she was at high school. We are happy to accept that Carl Bernstein was not motivated by sexism, and we are sorry for any embarrassment caused.