IN THE historic contest between a black man and a white woman, representing two groups who have never won a presidential nomination, to blame poor results on race or sex is taboo. Last week, for the first time, Hillary Clinton claimed that she faces deeper prejudice than Barack Obama. She was accused of pulling "the gender card" from the slim deck she still holds.

Obama reluctantly initiated a national conversation about race when Jeremiah Wright gave him no choice, but he rarely mentions the disadvantages he faces as an African-American running for office. Likewise, beyond promising to "break the highest and hardest glass ceiling" Clinton has previously avoided the suggestion that, as a woman, there are significant institutional barriers to her candidacy.

In an interview with the Washington Post on Tuesday, she argued that casual sexism is tolerated and occasionally promoted by the same media commentators who jump on any hint of racial prejudice. "There should be equal rejection of sexism and racism when it raises its ugly head," she said. "It does seem as though the press at least is not as bothered by the incredible vitriol that has been engendered by the comments by people who are nothing but misogynists It's been deeply offensive to millions of women."

This could be dismissed as a loser grumbling were it not so manifestly true. Clinton ran an incompetent campaign that ignored the caucus states, stressed experience over change and underestimated her opponent, but the pervasive gender bias she encountered didn't help. As Marie Cocco put it in the Post: "For all Clinton's political blemishes, the darker stain that has been exposed is the hatred of women that is accepted as a part of our culture."

Sometimes it was blatant, like the man who shouted "iron my shirt" at a town hall meeting in New Hampshire. Often it came from middle-aged white men likening Clinton unfavourably to their own wives and mothers. CNN's Jack Cafferty called her a scold. A Fox News pundit said: "When men hear Hillary Clinton speak, they hear, take out the trash'." Conservative talk show host Rush Limbaugh wondered: "Are Americans ready to see a woman president such asHillary Clinton age before their very eyes?"

MSNBC's Chris Matthews, one of the most respected news presenters in America, said: "The reason she's a US senator is her husband messed around she didn't win there on merit, she won because everyone felt my God, this woman stood up under humiliation'."

Her defenders, among them feminist icons Gloria Steinem and Robin Morgan, have vehemently objected to the double-standard, but until now Clinton herself has been less forthright. Her victory speech in Kentucky about "all of the women I've met who were born before women could vote" was a direct appeal to her most loyal constituency.

Obama has been careful to avoid alienating her supporters. A plan to declare victory after the Oregon primary, based on his insurmountable lead in pledged delegates, was shelved, to avoid the impression of pushing Clinton out of the way prematurely.

Instead, he spoke only of being "within reach of the Democratic nomination" and posed as a defender of women's rights. "No matter how this primary ends," he said, "Senator Clinton has shattered myths and broken barriers and changed the America in which my daughters and yours will come of age."

Resentment at the way Clinton has been treated is a worry for Democrats. Ellen Malcolm, founder of the feminist interest group Emily's List, observed that "the first woman ever to win a presidential primary is supposed to stop competing, to curtsy and exit stage right". Members of Clinton Supporters Count Too are threatening to withhold their votes if Obama is the nominee.

Republicans are alive to the opportunity. When Obama superdelegate Steve Cohen compared Clinton to the bunny-boiling character played by Glenn Close in Fatal Attraction, John McCain's press team rushed out a critical email. He hopes women will forget the campaign stop in South Carolina where he was asked: "How do we beat the bitch?" Once he stopped laughing, he answered "that's an excellent question".

If Clinton can be persuaded to drop out gracefully before the convention (something the Democratic rules committee could hasten by allocating Florida and Michigan's delegates) Obama can stress his feminist credentials. Last week, abortion activism group Pro-Choice America endorsed him as "a strong advocate for a woman's right to choose throughout his career in public office".

McCain, by contrast, has sworn to be "a loyal and unswerving friend of the right to life movement", raising the possibility that landmark abortion ruling Roe versus Wade could be overturned by an increased conservative majority in the Supreme Court.