SIOUX FALLS, S.D. — It takes spunk for Katie Andert to sit in the middle of the Commons, day after day, behind a table festooned with signs demanding "Vote No on 6: Repeal the Abortion Ban."

South Dakota is a distinctly conservative state, and the vast majority of its residents will tell you they are "pro-life." They'll also tell you South Dakotans prize politeness and eschew confrontation. Andert's booth on the Augustana College campus is a bit too in-your-face for most folks.

But Andert, a 21-year-old psychology major, is part of a historic campaign to overturn the nation's toughest anti-abortion law in a statewide referendum Nov. 7. The outcome of the campaign, which dominates the pre-election landscape in South Dakota, could help determine the future of abortion rights nationwide.

Supporters of the state's near-total ban on abortion hope to use it to overturn Roe vs. Wade, the 1973 Supreme Court decision that established a woman's constitutional right to terminate a pregnancy. Other states are poised to enact similar laws if this vote succeeds. If it is upheld, Planned Parenthood, which runs the only abortion clinic in the state, has said it will sue to block it in court on grounds it is unconstitutional.

"If they strike down Roe, all abortion is at risk in this country," said Eleanor "Ellie" Smeal, president of the Feminist Majority Foundation and publisher of Ms. magazine. "We estimate about 30 states would ban it."

South Dakota's law criminalizes all abortions except those "intended to prevent the death of a pregnant mother." It makes no exception for rape or incest, or for cases where the woman's health is at risk.

Dr. Marvin Buehner, an obstetrician in Rapid City, says the law would tie his hands when treating patients with serious medical complications.

Buehner recounted the case of a 38-year-old woman who was diagnosed with rectal cancer at the same time her 13-week pregnancy was confirmed. "The oncologist recommended radiation to the pelvis and immediate chemotherapy, which would have been fatal to the fetus," he said.

Buehner said the woman, whom he described as "pro-life," agonized over the dilemma but ultimately decided to abort "because she felt she had an obligation to her other children." Had the ban been in effect, Buehner said, he could have gone to jail for terminating the pregnancy.

"I would have had to prove my termination prevented her death," he said, "and I can't do that."

A small group of physicians who support the abortion ban argue that the law allows them to treat a pregnant cancer patient. The statute says medical treatment that results in the "accidental" death of a fetus is not a violation.