Albuquerque voters resoundingly rejected an antiabortion initiative Tuesday that would have banned the procedure after 20 weeks, with record-breaking turnout for a special election.

The nation's first citywide measure to limit abortion lost by nearly 10 percentage points, about 55% to 45%. More than 87,000 voters cast ballots, including 50,000 who voted early or absentee.

In all, about a quarter of the city's approximately 360,000 registered voters participated, a record for a special election, officials said. By contrast, last month's mayoral election drew about 70,000 voters.

"Albuquerque families sent a powerful message today: They do not want the government interfering in their private medical decisions," Micaela Cadena of the Respect ABQ Women campaign said in a statement. "Dangerous, unconstitutional laws like the one we rejected today have no place in Albuquerque, no place in New Mexico, no place anywhere in our nation."

Proponents of the measure said they were disappointed but would not quit.

"We're still going to be there for women and their unborn babies," said Maria Gallegos, a spokeswoman with Project Defending Life, an Albuquerque antiabortion organization.

The initiative turned Albuquerque into the latest battlefield on the contentious issue, as well as a testing ground for whether abortion limits could be imposed at the local level. The graphic campaign included a protest comparing abortion to the Holocaust.

The initiative was sparked by Tara and Bud Shaver, who call themselves pro-life missionaries. They moved to New Mexico from Kansas, a center of antiabortion activism, intending to mobilize a campaign to shut down Southwestern Women's Options, one of a handful of clinics in the country that provide later-term abortions.

After the election results had been tallied Tuesday night, Tara Shaver said: "When we moved here three years ago, our goal was just to bring awareness to what was happening here. This is a little deviation from that. We're going to move forward and keep focusing on that and keep strengthening our effort in the streets.

"We'll never back down. We'll never be silent. We'll never give up," she said.

To get the measure on the ballot, antiabortion groups gathered 27,000 signatures, more than twice the number required.

Shaver has said that although terminations after 20 weeks account for about 1.3% of all abortion procedures, banning them would be one step toward outlawing the practice entirely. There doesn't seem to be a consensus on when a pregnancy is considered late-term. Definitions range from the 20th week of gestation to the 27th.

The landmark 1973 U.S. Supreme Court decision that legalized abortion, Roe vs. Wade, has been interpreted to mean that abortions can be performed through 24 weeks of pregnancy.

But states have tried to chip away at the ruling.

Earlier Tuesday, the Supreme Court refused to block a Texas law while opponents appealed a lower-court ruling. That legislation requires each clinic performing abortions to have a doctor on staff who has admitting privileges at a hospital within 30 miles. Abortion rights advocates say one-third of the state's 36 abortion clinics will have to stop offering the procedure.

Albuquerque's "Pain Capable Unborn Child Protection Ordinance" needed a simple majority to pass. The only exception to the 20-week ban would have been for women whose lives would be in danger if they were to carry the fetus to term. There were no exceptions for rape or incest.

In a sense, Albuquerque voters were representing the entire state. The only late-term abortion providers in the largely rural state are in Albuquerque. Some out-of-state women also fly in for the procedure.

Abortion foes made it clear they would continue the fight. Father Frank Pavone, national director of Priests for Life, wrote an open letter to antiabortion activists, telling them to keep their hopes up.

"Pro-lifers in Albuquerque and elsewhere should not feel discouraged about the defeat of the effort to protect unborn babies from 20 weeks forward," he said in a statement. "It is a brilliant strategy, and we will see to it that this effort is introduced in other cities and states."

cindy.carcamo@latimes.com