THE clinic stands on a bleak, windswept road leading out of town to the endless prairie beyond. Its chunky brick walls protect against bombs. The high, slit-like windows foil snipers. Patients enter by the back door, hidden from public sight.

Sioux Falls Planned Parenthood is the last abortion clinic in South Dakota. There used to be two, but one doctor died, another retired and there was no-one willing to risk the growing violence against abortion doctors.

Now doctors fly in from neighbouring Minnesota, stay as long as they need to treat patients and then fly out.

Outside the clinic protesters hold a “silent prayer siege”. And if they have their way, it will close. It is under siege not just from prayers, but also from the law. Earlier this year the state assembly voted to ban abortions, with no exception other than the imminent death of the woman — not even for rape and incest.

The law was deliberately provocative, passed in the hope of goading pro-choice campaigners into challenging it. That, the anti-abortion movement hoped, would send the issue all the way to the Supreme Court with the ultimate goal of overturning Roe vs Wade, the landmark ruling that legalised abortion. Abortion rights activists have indeed challenged the law. It will go before South Dakotans in a referendum on November 7 — midterm election day.

South Dakotans are a warm but private people and the spotlight has been disquieting. A majority call themselves pro-life, in favour of a ban on abortion, but the prospect of a ban that would force a pregnant rape victim to carry her attacker’s child exposes moral complexities that even faith cannot always answer.

“I’m a Catholic and I don’t think abortion is right,” Patty, a farmer’s wife, says uneasily. “But when I think that could be my daughter . . . well . . . ” One poll puts the gap between the two sides at just four points.

The emotions involved have made for unusual campaigning. Attuned to the values of this conservative religious state, the “no” campaign, championing abortion rights, has avoided the right to choose in favour of a plea on behalf of rape and incest victims. “This law simply goes too far,” one poster reads.

The “yes” campaign is also carefully pitched. There are no posters of dead foetuses and little talk of God. Instead, it is of a woman’s right to motherhood, taken from her by men who pressure her into a procedure she will certainly regret.

“Abortion hurts women,” Leslee Unruh, the campaign’s manager asserts. “It’s the right of a woman to have a relationship with her child.”

One of her posters is of a girl who was raped, refused the morning-after pill and gave birth to a girl she has no regrets about keeping. Ms. Unruh is proud of her, but does not want to dwell on rape. “It’s so rare anyway,” she says.

So why not allow an exception? “Rape victims have options; they can get emergency contraception. If they have abortions, then the men just get away with it.”

Abortion rights campaigners believe they can win this vote because of the law’s harshness, but the might of the “yes” campaign is vast, backed by Catholic and evangelical churches, and the campaign is getting nasty. Even children are involved.

Kate Looby, Planned Parenthood’s director in the state, knows this too well. A friend of her seven-year-old son told the boy: “Your mom’s a baby killer.” Her 14-year-old daughter confessed that her defeat for school president followed a whispering campaign about her mother’s job.

For Ms Looby, a long-time defender of reproductive rights, these are depressing developments: “Most of the women we treat here are poor, they are already parents, they know what they are doing.”

Beyond the state borders others watch for inspiration for their own battles to bring down Roe v Wade.

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