In the heady atmosphere of last week's Republican convention – electrified by Sarah Palin's barnstorming speech as the vice-presidential candidate – a curious fact seems to have been overlooked. On paper, the new darling of Christian conservatives ticks all the right boxes as only a media-taunting, oil-drilling, gun-toting, abortion-hating, creationist mother of five could. Equally at home posing for photographs with her children and dead animals, she sends out an irresistible mating call to evangelical voters who suspect that John McCain is secretly too secular for their taste.
Did his team carry out sufficient checks before selecting an inexperienced state governor no one outside Alaska had heard of until 10 days ago? Who cares, when everyone is talking about this thrilling new player in the presidential contest.
But two months of hard campaigning lie ahead, and it's already beginning to dawn on smarter commentators that Palin is a terrible advert for conservative values. Last week, the Democratic candidate, Barack Obama, responded to the news that Palin's 17-year-old daughter was pregnant with an instruction to his supporters that the subject is off-limits, and a reminder that his own mother was only 18 when he was born.
Ms Palin insisted it was a private matter, although she was quite happy to parade her children, including the pregnant Bristol and her deeply uncomfortable boyfriend, at the convention in Minneapolis-St Paul.
Both candidates got it wrong: Palin, by exposing a troubled teenager to the world's media; and Obama, for failing to raise a legitimate and important issue.
He should have said that while the girl is entitled to privacy, it is clearly better in principle for young adults to finish their education and make decisions about marriage and children without the pressure of a teenage pregnancy; he should also have pointed out that Palin opposes any form of sex education that isn't "abstinence-based".
In practice, this means giving teenagers as little practical information as possible, while telling them not to have sex before marriage.
It it doesn't work – neither for Bristol Palin, nor for the other 750,000 teenage girls who get pregnant in the US each year at a cost of $9.1bn (£5.2bn) in public funding.
Last year, the British Medical Journal listed abstinence-based sex education programmes under the unequivocal heading "popular interventions that do not work"; an analysis of five such programmes showed, at best, no effects on teenage pregnancy rates and "at worst, an increase in the number of pregnancies in the partners of young male participants".
The United States has one of the highest rates of teenage pregnancy in the developed world, even worse than the UK, which is itself frequently criticised for having the worst record in Europe. Between 2000 and 2005, there were 44 births for every 1,000 women aged 15 to 19 in the US, compared with 27 per 1,000 in Britain.
More than 80 per cent of births to American teenagers are unintended, according to the Centers for Disease Control and Prevention, and they are powerful evidence in favour of broadly based sex education linked to programmes that provide contraceptive devices.
McCain has chosen a running mate who doesn't want that, even though her own family provides living proof of the failure of one of the main planks of her brand of social conservatism.
As if that were not bad enough, she is implacably opposed to abortion, even if it's the result of incest or rape. She wants to overturn the landmark legal decision Roe vs Wade, which legalised abortion in the US, even though in the past McCain has admitted that it would immediately lead to thousands of back-street abortions.
"Change is coming," he announced in his own speech to the convention, but the kind of change championed by Palin ought to make enlightened voters shudder.
Forget her populist oratory and feisty delivery: this is an old-fashioned, right-wing woman who has nothing to offer either secular Republicans or the disillusioned supporters of Hillary Clinton.
The former Miss Wasilla 1984 belongs firmly in the tradition of American arch-conservatives. These include Phyllis Schlafly, known for her opposition to feminism and the Equal Rights Amendment, and Anita Bryant – another former beauty queen, as it happens –, even if Palin has managed to persuade some over-excited columnists that having a job and five children is the pinnacle of modernity.
If McCain's calculation really was that his choice of a female running mate might tempt disillusioned Clinton voters away from the Democrats, it would have to count as one of the most insulting political gestures of the 21st century; women are not a tribe, so bowled over by a candidate who shares their gender that they will vote for her, regardless of her policies.
In democratic systems, politics often throws up women like Sarah Palin. They look and sound very different from the men around them – Palin seems to have taken a conscious decision to wear skirts, unlike Hillary Clinton and her jokey "sisterhood of the travelling pantsuit" – but their agenda is even more anti-feminist than their male peers.
That's why they get so far, even if their supporters sometimes underestimate the reach of their ambition.
Members of the Conservative Party in Britain were not universally thrilled in 1975 when Margaret Thatcher successfully challenged a former prime minister, Edward Heath, for the leadership. Baroness Thatcher, as she now is, identified so strongly with men that she included only two women in her Cabinet during her time as prime minister. In so doing she created such a dearth of female experience in the Conservative Party that her successor, John Major, did not put a single woman in his first cabinet.
That is what makes right-wing women so dangerous to other women. They have perfected the trick of stamping a feminine image on male power and selling it as something new, when what they are in reality the most fervent upholders of the status quo or even determined – as Palin is over reproductive rights – to turn the clock back.
I'm always surprised that this paradox isn't immediately visible to seasoned political commentators, who should have observed it often enough by now. It may be that the gushing, awestruck commentaries on Palin's performance in Minneapolis will give way over the next eight weeks to a more sober assessment of her candidacy, especially when she faces her much more experienced Democratic opponent, Senator Joe Biden, in a televised debate.
In the meantime, it speaks volumes that the only woman in this crucial presidential contest is the beneficiary of patronage, hand-picked rather than elected, and the holder of startlingly reactionary views. The American electorate is allowed to vote for Sarah Palin, if it so wishes, but not Hillary Clinton: patriarchy still rules OK.
For rolling comment on the US election visit: independent.co.uk/campaign08
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