When the United States Supreme Court overturned Roe v. Wade last summer, advocates on either side presumed that the country would divide along the bright color lines: red states completely banning abortion, blue states protecting it.

That prediction failed to anticipate the Sister Senators.

The Sisters, as they call themselves, are the women in the South Carolina State Senate — the only women, three Republicans, one Independent and one Democrat, in a legislature that ranks 47th among states in the proportion of women. As a block, they are refusing to allow the legislature to pass a near-total ban on abortion, despite a Republican supermajority.

Three times in eight months, Republican leaders in the chamber have tried to ban abortion beginning at conception. Three times, the women have resisted, even as fellow Republicans have threatened primary challenges and anti-abortion activists have paraded empty strollers and groups of children heckling the women as “baby killers.”

Before the most recent debate started in April, the anti-abortion group Students for Life dropped off gift bags at the offices of the three Republican women containing plastic spines, infant size but intended to encourage the women to grow one, with notes signed, “the pre-born.”

The women filibustered, taking the gifts to the podium on the Senate floor to declare themselves even more firmly in resistance. “I’ve got one hell of a spine already, but now I’ve got another backup,” Senator Katrina Shealy said, flanked by the two other Republican women, all holding their plastic spines like trophies.

After three days of debate, during which the women spoke for as long as four hours each at a time, Senate leadership acknowledged — again — that it did not have the votes to pass the ban.

“I don’t think the Republican Party saw us coming, because we didn’t do what they thought we were going to do,” Ms. Shealy, the senior member of the group, said in an interview with the other women around a table in her State House office. “They thought we would do just what they told us to do.”

But as men argued that abortion was killing babies, the five women insisted that abortion bans are not about saving lives but controlling women — and that they will not be controlled. They have argued the ban reduces women to “baby machines” like the dystopia of “The Handmaid’s Tale” and rejected as ludicrous claims from male legislators that women use abortion as birth control.

“I don’t believe any woman goes out on Friday night and has sex and gets pregnant so she can have an abortion the next day,” Ms. Shealy said.

The debate in South Carolina, a deeply red state where abortion for now remains legal up until 22 weeks, shows how much has not happened according to plan now that overturning Roe has made abortion bans a reality rather than a symbolic gesture or plank in a party platform.

Many Republican-controlled states have outlawed abortion, largely through bans triggered by the Supreme Court decision in June. But states that were expected to have not, stopped by voters in ballot measures (Kansas and Kentucky), Republican legislators (South Carolina and Nebraska) or courts that have temporarily blocked bans, saying they are likely unconstitutional (Utah and Wyoming).

“Pro-life” and “pro-choice” have proven muddy if not increasingly meaningless distinctions. And views on abortion have turned out to be far more nuanced than a red/blue divide: Polls show groups that might have been expected to generally back bans on abortion, Republican women among them, moving away from a desire to make most abortion illegal. Even in South Carolina, polls show most voters support some abortion access and disapprove of overturning Roe.

“There’s got to be gray area,” said Senator Penry Gustafson, another of the Republicans.

The three Republican women are white, the two others Black, and all describe themselves holding deep religious faith. They are all mothers, and several have fostered children or supported relatives or other young people through college, and they say their experience of pregnancy informs their views on abortion.

All the women support the right to abortion, but with some restriction, though they vary on gestational limits: Senator Margie Bright Matthews, a Democrat, and Senator Mia McLeod, who left the Democratic Party this year, lean toward codifying Roe, which allowed some right to abortion up until fetal viability, around 24 weeks.

Ms. Gustafson and Sandy Senn, the third Republican, would prefer to restrict abortion after the first trimester, with exceptions. Ms. Shealy said if it were up to her personally, she would leave the decision to women, their partners and their doctors: “Women know what’s best for their bodies.”

Still, she and other Republican women describe themselves as pro-life, not pro-choice. They proudly embrace the state’s Republican creed, which begins “I do not choose to be a common man” and includes a pledge “to think and act for myself.” They also believe that women should be allowed to think and act for themselves, and that most would say that the decision on abortion should be left up to them.

“There are millions of women who feel like they have not been heard,” Ms. Gustafson said during their filibuster last month. “And that’s why I’ve been standing up here this long.”

Their positions hardly make them champions to reproductive rights groups. All three Republicans voted in favor of a six-week ban, which the Senate passed. This is before most women know they are pregnant. The Republican women successfully insisted on adding exceptions for medical emergencies or cases of rape, incest or fatal fetal anomalies.

They call it a compromise between the ban at conception and bills they put forward that would have placed the question of abortion rights to voters on the ballot, or banned abortion after the first trimester, with exceptions. The Republican leadership in the Senate declined to put those measures to a vote.

The House has refused to vote on the six-week bill, holding out for the ban at conception, but still has until Thursday to do so. Instead, it has pressured the Senate to repeatedly vote on the ban at conception. Senate leadership has done so, despite having acknowledged it did not have the votes.

“If they had done it the one time, that’s one thing,” Ms. Senn said. “But then a second time and a third time. They knew what the outcome was going to be. They were forewarned.”

“It’s like they dared them,” agreed Ms. Matthews.

“I’m like, you’re going to get it,” Ms. Senn added. “You’re going to get an earful.”

An earful she delivered: “We the women have not asked for, nor do we want, your protection,” she said, addressing her male colleagues on the floor, wearing flip flops for comfort during the filibuster. “We don’t need it. We don’t buy into the ruse that what you really want is to take care of us.”

Ms. Gustafson, elected in 2020, got her first taste of politics when a friend took her to a Tea Party rally in 2016. She had owned a restaurant and acted in community theater, including in the role originated by Dolly Parton in the classic film about strong Southern women, “Steel Magnolias.”

Banning at conception “allows nothing for the in-between or things we can’t even conceive of,” she said. “There are too many things that can happen.”

The women have found support from one or two male Republicans in the chamber. But others have accused them of betraying the party by seeking bans short of one starting at conception.

“I’m not willing to sit by and let the goal posts be moved for what it means to be pro-life for the Republican Party,” Senator Richard Cash said.

As other states in the region have restricted abortion, the Republican women worry that South Carolina has become a destination for it. The number of abortions has risen since Roe was overturned, and nearly half are women coming from other states, according to state figures.

The South Carolina legislature is an unexpected place to find so much talk of women’s rights. It took until 1969 to formally ratify the 19th Amendment, which gave all American women the right to vote in 1920.

Abortion rights supporters were shocked in January when the state’s highest court declared that privacy protections in the state Constitution extended to a right to abortion, overturning a six-week ban with limited exceptions.

That opinion was written by the only woman on the court, who has since retired, and the legislature replaced her with a man. The Republican leadership is trying to pass the new six-week ban in the hopes the new court will overturn the decision.

Both Ms. Shealy and Ms. Gustafson knocked off popular incumbents to win their seats; Ms. Shealy ran as a petition candidate against a Republican, and wore bedazzled Wonder Woman sneakers to win it. (“I still wear them when I get mad,” she said.) A newspaper editorial at the time accused her of an “over-eager desire to be liked.”

For three years, she was the only woman in the chamber, and leaders continued to address the body as “Gentlemen of the Senate.” One Republican colleague said women should be barefoot and pregnant, not in the legislature, and later told her women were a “lesser cut of meat.”

Now chair of the committee on family and veterans’ services, Ms. Shealy is the self-described “Mama Hen” of the five women. “Come girls,” she said, herding them to a photograph, “Chop chop.”

Female legislators are still unusual enough to attract attention. “The women!” a lobbyist exclaimed as the quintet passed him on the escalator. “I need to go with y’all!”

A parent in the Upstate region of South Carolina objected to “The Handmaid’s Tale” in a school library after Ms. Senn mentioned the book during the filibuster. But she and the other senators say most of their constituents agree with them. Older women in particular, Ms. Senn said, have sent notes with small donations. “One of them said, ‘This old crone is proud of you.’”

And women who staff the legislative offices have flashed them thumbs up. One stopped Ms. McLeod as she got out of her car on Wednesday. “She said thank you for what you did last week,” she said. “Many of them work for Republican men.”

Ms. Matthews added: “They always say, ‘We can’t say what we think.’”