In a surprising decision last week, Nebraska lawmakers overturned the governor's veto and voted to abolish the death penalty.

In the wake of the decision, one seemingly counter-intuitive thread has caused speculation to flourish: what was the impetus behind Republican lawmakers' motivation to override a Republican governor's veto in an unabashedly red state, ending a practice that has become nearly synonymous with hard-line conservatism? To some, it was a sign-of-the-times decision following a number of horribly botched, high-profile executions. But to others, it signaled that the death penalty could be singing its swan song, even in the minds of the nation's right-wingers.

According to Robert Dunham, executive director of the Death Penalty Information Center, a non-profit that focuses on capital punishment, Nebraska could be a case study at a time when the practice seems more unpopular than ever.

"What's happened in Nebraska is a microcosm of what's happening across the United States, where there's been a steady national trend away from the death penalty," Dunham told ATTN: in a phone interview. "One of the notable things about the repeal in Nebraska is that it provides evidence of the growing, outspoken opposition to the death penalty among philosophically conservative legislators...and what they had to say about the death penalty is instructive about trends in the United States," he said.

Dunham told ATTN: that nationwide polls show support for capital punishment is at a 40-year low, and even its application has dropped significantly, despite some high-profile cases in recent months, such as that of the Boston marathon bomber, Dzhokhar Tsarnaev. "Last year, there were fewer executions that there had been in 20 years, and...fewer [inmates] sentenced to death than anytime in the past 40 years."

External factors influence popular support of the death penalty.

Most states at least have the option of capital punishment on the books, and public opinion, despite a general sloping trend, swings back and forth. According to Dunham, public support can vary under the influence of different external factors. A cultural sense of fear, like the red scare of the last century, or of high-profile killings, like those of Martin Luther King Jr. and Robert F. Kennedy can push people to favor the death penalty: it swelled around those events, he told NPR. But public distrust of the government can have the opposite effect, as it did in during the Vietnam War. By the same token, he said that when the public perceives less violence, learns about wrongful convictions and the more than 150 exonerated death row inmates, or examines the cost, support tends to drag.

A broader shift.

Recent trends aside from public opinion also show that there are strong signs of change nationwide. Four different states––Colorado, Oregon, Pennsylvania, and Washington––have imposed moratoriums on the practice, repeal measures in other states are finding support––a measure in Delaware was shut down with just one vote last month––and half a dozen states who employ the practice haven't used it in more than a decade, the LA Times notes. Nebraska, which has executed three people since 1976, marks the the 19th state––along with Washington, D.C.––to formally abolish the death penalty, and the seventh to do so in the past decade. The last conservative-leaning state to do so was North Dakota, in 1973.

Why are conservatives opposing the death penalty?

National trends, according to Dunham and other experts, echo the gradual shift among some conservatives with whom the death penalty is falling out of favor.

"For many years, people have thought about the death penalty in the abstract––is it philosophically justifiable––and didn't go beyond that. What we saw from the conservatives [in Nebraska] was that they were discussing the death penalty as a government policy, understanding that policies don't live in the abstract; they live in real time, and in evaluating them, you have to take a look at how they perform in practice," said Dunham.

As the Marshall Project points out, death penalty cases are getting more and more expensive to mete out, as elongated litigation and time spent on death row––which is more expensive than standard lock-up––snowballs over the years it takes for a capital punishment case to run its course. Attorney fees, use of experts of specialists, ever-changing laws, juries, and housing costs add up and only get more expensive as time goes on. A 2010 U.S. Judicial Conference report found the median cost for a litigated federal death penalty case went from $269,139 between 1989 and 1997 to $620,932 between 1998 and 2004.

Moreover, numbers show that it can be cheaper to house inmates for life than to put them to death––a financial interest that happens to line up with public opinion polls.

On top of baseline costs, there are factors that make the practice morally uncomfortable, like the possibility that innocent people mistakenly placed on death row could be executed or that in the absence of traditional lethal injection drugs, states could use less-tested drugs or methods––the subject of a Supreme Court case which could further shake up the nation's death penalty practices. (Nebraska Gov. Pete Ricketts (R) said he has secured a source of lethal injection drugs and that his state's repeal of the death penalty would not stop his administration from executing the 10 death row prisoners on the docket.)

But all those concerns line up with Republican ideals, according to Marc Hyden, national advocacy coordinator for Conservatives Concerned About the Death Penalty. In fact, Hyden says the death penalty is completely out of line with the bedrock pillars of modern conservatism.

"I think that the conservative case against the death penalty couldn't be simpler," he told ATTN: over the phone. "It risks innocent life, so it's not pro-life; it costs more than life without parole, so it's not fiscally responsible; and I don't believe that giving an error-prone state the power to kill its citizens is a form of limited government."

"To see a state-–a very conservative state like Nebraska––rid itself of the death penalty doesn't surprise me," he continued. "This is what conservatives are elected to do...repeal broken, wasteful government programs. I think that for a long time conservatives bought into this mindset of a so-called 'tough on crime' mindset that's led to, really, a disaster in our criminal justice system. Essentially it's in our principles to oppose the death penalty because it's antithetical to our ideals."