Almost immediately, Democratic presidential candidates lined up in support, calling capital punishment a moral outrage infected with racial bias. Sen. Kamala Harris of California, a former prosecutor, called for a federal moratorium on executions. Former Rep. Beto O’Rourke of Texas did the same.

The moment marked a generational shift for a party where some candidates long supported the death penalty to protect themselves from being portrayed as soft on crime.

But Democrats aren’t leading a national debate; they are following a decadeslong trend that has seen support for the death penalty drop from nearly 80 percent in the 1990s to just over 50 percent now.

Still, many feel that Newsom was doing his party no favors politically by forcing Democrats to talk about an issue that can still be fraught in a general election. Even in solidly Democratic California, voters in 2016 rejected a ballot initiative to end the death penalty and instead approved one to expedite executions.

In short, the moment captured what has changed significantly and what has not with an issue that is hard-wired into the nation’s psyche. Like the proliferation of guns, capital punishment distinguishes the United States from other Western democracies, virtually all of which have banned it.

Bill Whalen, a research fellow at the Hoover Institution who once advised Pete Wilson, a Republican former governor of California, wrote in a column: “Every Democrat who wants to unseat President Trump now must figure out where they stand on the death penalty.”

He continued: “For some triangulating Democrats, that’s a tricky balancing act given that capital punishment is despised by the party’s progressive base but is far more popular in the crime-and-order Heartland.”

The new attention notwithstanding, presidents are limited in their power over capital punishment, several experts pointed out in interviews. A president could clear federal death row, but that includes only 62 people compared with more than 2,500 condemned inmates in state prisons.

The federal government has executed only three people since it reinstated capital punishment in 1988 — one of them was Timothy McVeigh — and the last one was in 2003.

The president has far greater power to determine the future of capital punishment in the United States by appointing justices to the Supreme Court. Experts expect the court to eventually rule on whether the Constitution allows executions at a time of increasing recognition of the enormous financial costs of the death penalty, high-profile exonerations and research showing persistent racial bias in capital cases.

“The president, and what the president does, will bear very much on the Supreme Court’s thinking on this, because the president does reflect the national electorate,” said James S. Liebman, a professor at Columbia University who specializes in the death penalty.

— New Positions and Different Risks

You don’t have to look back very far to see what a shift there has been in the positions taken by Democratic candidates.

In 2016, for the first time, the Democratic Party platform called for the abolition of the death penalty. But Hillary Clinton, the party’s nominee for president, supported capital punishment. President Barack Obama never called for its end, either. Al Gore was a supporter, and so was Bill Clinton.

Some fear it could still be a losing issue in a general election against President Donald Trump, who has talked about expanding those eligible for execution to include convicted drug dealers and could use the issue to rally his base and portray Democrats as weak on crime.

In a Twitter post about Newsom’s moratorium, Trump wrote, “friends and families of the always forgotten VICTIMS are not thrilled, and neither am I!”

The issue illuminates ideological and generational divides among many Democratic voters. Many of the presidential candidates are on record opposing capital punishment; Joe Biden, the former vice president who is expected to enter the race in the coming weeks, has supported it.

As a senator in the 1990s, Biden supported many get-tough-on-crime policies that liberals now disavow, including limits on appeals for death row inmates.

“Biden was one of the major proponents of the 1994 amendments that severely limited the ability of death row prisoners to obtain meaningful judicial review,” said Robert Dunham, executive director of the Death Penalty Information Center, a nonprofit group that provides analysis and information on capital punishment. “Other people who have sponsored that bill have said they thought that was a mistake. And I think that voters will have to decide whether candidates for office have made mistakes and learned from them, or whether they are professing new views because the views of the public have changed.”

While Harris has long opposed capital punishment, she has a somewhat complicated history on the issue. As the district attorney in San Francisco, she refused to seek a death sentence for a defendant accused of murdering a police officer, provoking outrage from the right. But she defended California’s death penalty as the state’s attorney general, and twice, in 2012 and 2016, she refused to take a stand on ballot initiatives that proposed to abolish it.

Aside from Biden, most of the other candidates have opposed the death penalty. In addition to Harris and O’Rourke, who have said they would support a federal moratorium, Sens. Bernie Sanders, Cory Booker, Elizabeth Warren and Kirsten Gillibrand all said they support Newsom’s moratorium. Two others in the race — John Hickenlooper, former governor of Colorado, and Jay Inslee, governor of Washington — imposed moratoriums in their states.

“It’s kind of interesting that they are talking about it because it had pretty much dropped off the radar for national campaigns,” said Kent Scheidegger, the legal director of the Criminal Justice Legal Foundation, a group based in Sacramento that has led campaigns in California and across the country in support of the death penalty. “I’d love to see it made an issue.”

He predicted that it may “drop back off the screen in the national campaign. I don’t think Democrats want this to be an issue in a general election, because it would be a loser for them.”

— Limiting Executions, but Not Ending Them

For all the shifts on the death penalty, its status now is defined by two things. The Supreme Court, which determines its legality, seems firmly in favor of it. And at the state level, where prosecutors, jurors and local courts administer the justice system, the number of death sentences and executions is plummeting.

A very different Supreme Court declared executions unconstitutional in 1972, saying the arbitrary use of capital punishment constituted “cruel and unusual punishment” under the Eighth Amendment. Four years later, after states began remaking their death penalty systems, the court ruled that executions could resume. (The first new federal death penalty statutes were approved in 1988.)

Executions soared during a period of high crimes rates in the 1980s and 1990s. The high point for death sentences was 1996, when 315 people were condemned to die. In 1999, 98 people were executed, the most in any year since 1976.

Since then, as crime has fallen, the number of new death sentences dropped to 31 in 2016, a modern-era low, and 20 states have ended the practice.

In three important cases in recent years — in 2002, 2005 and 2008 — the court has narrowed the death penalty’s scope, ruling that juveniles and those with intellectual disabilities can’t be executed, and limiting the types of crimes — mostly only murder — that are eligible for a capital sentence.

But the court — with two new conservative justices appointed by Trump, Neil Gorsuch and Brett Kavanaugh, and a 5-4 conservative majority — is seen as solidly behind the death penalty.

That was vividly illustrated by a bitterly divided recent case in which the court ruled 5-4 to allow the execution of an inmate in Missouri who said a rare medical condition would make him choke on his own blood during his lethal injection.

Gorsuch, writing for the majority, said the Eighth Amendment “does not guarantee a prisoner a painless death.”

If Trump is able to nominate additional justices who are confirmed, his successor’s influence on the death penalty would be limited to enacting a federal moratorium, nominating district court and appeals court judges and using the bully pulpit to make a case against capital punishment.

— ‘The Most Toxic Issue’

The death penalty has long played a powerful role in presidential politics, especially in the 1980s and 1990s.

It helped sink the candidacy of Michael Dukakis, a Democrat, in 1988 when he said in a debate that he would oppose an execution even if his wife, Kitty, were raped and murdered.

Four years later, Bill Clinton rushed back to Arkansas from the campaign trail to oversee the execution of a mentally disabled man convicted of killing a police officer, burnishing an image of being tough on crime.

“It was just the most toxic issue,” said Stephen B. Bright, a professor at Yale Law School, who noted that during this time many state judges were removed from office for their opposition to the death penalty. Gov. Mario Cuomo of New York lost his re-election bid in 1994 partly because he was against capital punishment, Bright said.

Now, the politics have shifted. Not only are Democrats more willing to speak out against the death penalty, but many Republicans — though not Trump — are turning against capital punishment on limited-government grounds and, especially, because of high costs.

One study has shown that capital punishment has cost California $5 billion since the 1970s. Another study, by Ernest Goss, an economics professor at Creighton University, found that each death penalty prosecution in Nebraska cost $1.5 million more than when prosecutors sought life without parole.

Those more complex realities do not negate the potential for contentious politics in 2020.

“I think the Democratic primaries may be the first one in which candidates outflank one another on the left on criminal justice issues,” said Carol S. Steiker, an expert on the death penalty at Harvard Law School.

But while Democratic candidates would likely appoint judges and officials who support criminal justice reform broadly, few expect the death penalty to become a litmus test issue like abortion.

And it’s not clear what will carry more weight in 2020 politics — the complex realities of the justice system or the history of the death penalty as a potent political weapon, particularly in the hands of Trump.

“You’ve already got socialism and immigration, and you can add this to it,” Bright said. “The question is if it will resonate.”

This article originally appeared in The New York Times.