Colby Coash can point to the moment that his evolution in thinking about the death penalty began.

It was September 3, 1994, and Coash — now a conservative senator in the Nebraska legislature but then a freshman at the University of Nebraska-Lincoln — decided to go with some friends to the state penitentiary. Willie Otey, convicted of first-degree murder, was set to be executed at midnight, and people were gathering in the parking lot outside. Coash can still remember the scene: the live band, the grilling meat, the revellers popping cans of beer and chanting “Fry him!”

Coash says now: “You wouldn’t have been able to tell the difference between the parking lot of the penitentiary and a tailgate [at an NFL game]. It was pretty ugly.”

Even though he went to the event as a supporter of capital punishment, he says: “It kind of changed my heart. I thought, ‘I don’t want to be a part of state-sponsored killing.’”

For much of the past 40 years, public support for the death penalty has been high, topping out at 80 per cent in 1994, according to Gallup polling. In the late 1980s and early 1990s, the death penalty was so popular that it was used as a political cudgel by Republicans looking to depict opponents as soft on crime. In the 1988 presidential race, Democrat Michael Dukakis was hammered by George H.W. Bush’s campaign and the media after he said at a debate that he would not support the death penalty, even if someone raped and murdered his wife. In 1992, candidate Bill Clinton, then Governor of Arkansas and looking to avoid a repeat of Dukakis’s trouble, returned to his home state to preside over the execution of a mentally disabled prisoner named Ricky Ray Rector. Since the Supreme Court legalised capital punishment in 1976, “most individuals of all political orientations were for the death penalty when asked the question in the abstract”, says Robert Dunham, executive director of the Death Penalty Information Centre.

But that has started to shift. presidential candidates Hillary Clinton and Donald Trump both support the death penalty — but Trump is much more enthusiastic, and Clinton has had to answer for her husband’s criminal justice policies during her primary campaign against Bernie Sanders. A Pew poll found that only 40 per cent of Democrats supported capital punishment last year, down from 71 per cent in 1996.

That same poll showed GOP support for the policy dropping ten points, from 87 per cent to 77 per cent, over the decade. Times are changing for conservatives, too, but for markedly conservative reasons.

In the past year, Republican lawmakers in red-leaning Nebraska, Utah, Missouri, Kentucky, Kansas, Ohio, Wyoming, Montana, South Dakota and New Hampshire have sponsored bills to repeal the death penalty. They are organising themselves in places such as North Carolina, Tennessee, and Washington State, too. Coash is now part of a small group of activists that argues that the best case against the death penalty is a conservative one — and that the best way to make progress on the issue is to convince other Republicans in red states, where the death penalty is, for the most part, uncontroversial.

After that night in Lincoln, Coash decided he could not support the death penalty as a pro-life Catholic. But it wasn’t until he made it into the Nebraska legislature in 2008 that he could do anything about it. For years, state senator. Ernie Chambers, a progressive firebrand from North Omaha, had been introducing Bills to stop the death penalty, but only twice — in 1979 and 1999 — had they passed, and both were promptly vetoed. In 2015, though, Coash sensed an opening. Although Nebraska’s legislature is technically nonpartisan, it is not difficult to tell that many of the members are, like their voters, Republicans — and voters had sent to the state House that year a group of freshman lawmakers, whom Coash figured might be open to his conservative arguments. So he began reaching out to his new colleagues, one by one, and asking them to sign on to Chambers’s Bill.

Coash realised that the traditional arguments against the death penalty — the potential for error; the way it is unevenly applied to poor, black and mentally handicapped defendants — were not working on conservatives. Those arguments, he figured, were too abstract for death penalty supporters, who looked to death row inmates and saw men whom they felt didn’t deserve their sympathy. So he tailored his approach. “I started to frame the death penalty in a different way, to change the narrative,” he says. “I used Republican principles to argue that this was a broken system.”

First, he made the case that the death penalty was costly and ineffective. Nebraska had spent an estimated $100 million on death penalty cases and executed only three people since the Supreme Court’s 1976 ruling that affirmed the constitutionality of capital punishment. Second, Coash argued, conservatives are supposed to be the party that pushes back against unjust overreach into individuals’ lives, and what would be a better example of that intrusion than potentially taking an innocent life through capital punishment? Third, he said, the families of victims — many of whom had testified before his committee that the endless appeals on death penalty cases were traumatising and unjust — deserved better. When asked to describe his position in personal terms, he said it was consistent with a promise that he made to always vote pro-life.

The debate on the Bill was long and emotional. But in May 2015, Nebraska’s legislature voted to repeal the death penalty, becoming the nineteenth state to ban it and the seventh since 2007. A week later, lawmakers wrangled enough votes to overturn Pete Ricketts’s veto. The governor has poured his considerable financial resources into a November ballot measure to reinstate it, but the efforts of Coash and his colleagues have turned Nebraska into a test laboratory for opposing the death penalty from the Right.

Religiously committed conservative activists have received a number of boosts over the past few decades, including Pope John Paul II’s declaration of Catholic opposition to the death penalty in 1995. (Pope Francis has been just as emphatic.) The past several years have also resulted in what Dunham calls the “innocence revolution” — more prisoners being exonerated; sometimes through new investigations, other times through DNA evidence — which has drawn attention to the potential for error. Dunham believes the resurgence of activist groups focused on limited government in the wake of the recession reignited the dialogue about the costliness of the policy. Younger voters, too, are slightly less likely to support capital punishment than older conservatives.

Last year, the National Latino Evangelical Coalition voted unanimously to oppose the death penalty. In October, the National Association of Evangelicals updated its 1973 resolution in support of the policy to acknowledge the opposition of some of its members.

To help reach pro-death penalty Republican voters, anti-death penalty conservatives are turning to people who can speak in ways that conservatives may identify with, even if these advocates are not, themselves, conservative — such as Christy Sheppard, a counsellor from Ada, Oklahoma, whose cousin, Debra Carter, was murdered in 1982. A few months ago, Sheppard travelled to Nebraska to tell the story of what happened after her cousin’s death. Five years after the slaying, police arrested two men, Ron Williamson and Dennis Fritz, and charged them with murder. Fritz received life in prison; Williamson was sentenced to death. For years the family were satisfied, even happy with the outcome — until DNA testing 11 years later proved that both men were innocent. The man eventually found guilty in Carter’s death, Glen Gore, was already in prison on other charges by the time a DNA test identified him. He walked away from a work crew after learning that he was a suspect in the 1982 murder, but turned himself in a week later. He was convicted in 2006.

Sheppard felt tremendous guilt over the ordeal that Williamson, who suffers from bipolar disorder, faced. “To think that we wanted him to die for a crime he wasn’t even guilty of — he didn’t even know her — is just horrible,” she says.

When anti-death penalty groups began asking her to tell her story, she says: “I felt like I couldn’t not say anything.”

But anti-death penalty conservatives are still working against broad support for capital punishment, especially among their fellow conservatives. Kentucky’s Bill failed by one vote to make it out of the House Judiciary Committee. In Utah, the Senate passed a Bill, but it was pulled from the House floor after leaders realised that it did not have enough votes. And in Nebraska, Ricketts and his billionaire father, TD Ameritrade founder Joe Ricketts, have invested hundreds of thousands of dollars backing November’s ballot initiative to bring back the death penalty. The group organising those efforts, Nebraskans for the Death Penalty, said in a news release last year that, according to its polling information, 64 per cent of Nebraska voters agreed with its position.

The thread running through Nebraska, Kentucky, North Carolina and other states where conservatives have been working against capital punishment is Conservatives Concerned About the Death Penalty, a group founded by Heather Beaudoin, a 31-year-old from Michigan with a background in conservative politics.

Beaudoin was raised in an evangelical family. She likes to say that her opposition to the death penalty is “of the Lord” because it is something she has felt passionate about since she was a little girl. After a brief stint in Washington, after college, Beaudoin moved to Montana to work for AmeriCorps, and one day, outside her office, the Montana Abolition Coalition held a rally with exonerees and their family members. Beaudoin landed a job with the coalition by suggesting that she lead outreach to evangelicals and the law enforcement community. After a few years, she went to Equal Justice USA, a group that works on criminal justice reform issues, to launch a national organisation aimed at conservatives. That turned into Conservatives Concerned About the Death Penalty.

Beaudoin reaches out to evangelical and other faith-based leaders and gets them talking about policy; her colleague, Marc Hyden, the group’s national advocacy co-ordinator, works with movement conservatives, college Republicans, tea party activists and libertarians.

“For me, it’s about redemption,” Beaudoin says. “That is true for most evangelicals as well. That’s at the centre of our faith. We believe in grace, we believe that God can do wonderful things. How can we say, ‘You are the worst of the worst, you are not worthy, and we will dispose of you?’ What does that say about us and what we believe?”

Hyden says he and Beaudoin have been surprised by how they have been welcomed at events such as the Conservative Political Action Conference and on conservative college campuses. “I’m finding that we are being accepted in some of the most conservative circles of America,” he says. Hyden, who previously worked for the National Rifle Association, frames his arguments to movement conservatives in a slightly different way than does Beaudoin. “There’s nothing limited about giving power to the state to kill you,” he says. Especially “if you don’t trust the Government to launch a healthcare site or deliver mail”.

But he understands as well as anyone that the journey to opposing the death penalty is a long and difficult one. “I used to support it, I’m a little ashamed to say,” Hyden says. “I was willing to violate my own conservative principles.”

The harder he looked at the issues, though, “the less I could justify supporting it. It risks innocent lives, there’s no way it’s pro-life and it costs more than life without parole”.

That kind of introspection, Coash and his allies say, is exactly what their side needs.

During the debate over the death penalty in Nebraska, Coash said, his father-in-law, a farmer, was shocked and asked him, “What the hell are you doing?” Coash laid out his case, landing on the state not having carried out an execution in 20 years. Coash says his father-in-law responded: “Well, shoot, get rid of it then.”

He knows that the pro-death penalty movement is formidable, but he remains hopeful.

“Nebraskans,” he says, “are very practical people.”

• Marin Cogan is a contributing editor for New York magazine, based in Washington