In modern times, the United States has never been as polarized and partisan as it is now. The two parties cannot work together and have stopped talking to each other, and many of their members barely see people in the other party as human. Adversaries become enemies; disagreement is seen as treason.

It’s time to meet Jordan Harris and Sheryl Delozier, members of the Pennsylvania House of Representatives.

Ms. Delozier is a Republican, representing parts of Cumberland County, near Harrisburg. Mr. Harris is a Democrat, representing a section of urban Philadelphia. The host of a political talk show in Harrisburg called them “the odd couple.”

Well, not completely. They are both passionate about, and remarkably effective at, improving the criminal justice system. Together, they were shepherds of the nation’s first Clean Slate Law, passed in 2018. It automatically wipes from public databases some 30 million Pennsylvania criminal records, allowing people who committed low-level crimes years ago — or were never convicted of anything at all — to get work and housing, to rebuild their lives.

Ms. Delozier and Mr. Harris also started a state criminal justice caucus. “The Judiciary Committee is one of the busiest,” Ms. Delozier said. “Jordan and I decided to work with senators and representatives, Republicans and Democrats, to vent through some of the legislation that’s been put out there. Let’s work through some of the bumps first and present something that’s supported.”

Ms. Delozier’s initial interest in criminal justice was inspired by the issue of victims’ rights, while Mr. Harris represents a largely low-income African-American area of Philadelphia hollowed out by over-incarceration.​

“On many issues we disagree and fight, but we’ve never been disagreeable,” said Mr. Harris. “We travel across the country to talk about criminal justice reform, and when we’re done, we hang out together. Sheryl and I are friends.”

Ms. Delozier’s husband is a police officer, and they talk about the price the police pay. They also talk about the price Mr. Harris’s constituents pay for over-policing. He admires her passion for baseball. She admires his dedication to his mother.

“It is un-American to think we can’t disagree,” Mr. Harris said.

Mr. Harris and Ms. Delozier work on the one issue in America that is truly bipartisan. Over the weekend, Benedict College, a historically black college in Columbia, S.C., hosted President Trump and Democratic presidential candidates in a forum on criminal justice. The Democrats each put forth their platforms to further reduce mass incarceration and its harms.

And then, being Mr. Trump, he moved on to claim that no other president had done as much as himself for black people. What was notable was that all the candidates, Mr. Trump included, competed for the mantle of biggest criminal justice reformer.

Across America, Democrats and Republicans demonize each other — and then sit down to hammer out legislation to reduce mass incarceration. Last December, Congress passed the First Step Act, which applies to federal prisons. It increases opportunities for education and rehabilitation in prison, gives inmates more time off for good behavior, requires prisoners be placed closer to their families, and reduces mandatory minimum sentences for some drug offenses.

But the real progress is in the states — a broad range of them. Texas, South Carolina, Georgia, Louisiana, Mississippi, Colorado, California, New Jersey and New York, among others, have all passed major criminal justice reforms.

This momentum shows what can be done. At the same time, it highlights the rarity of bipartisan progress.

So what is it about criminal justice?

It’s certainly not the case that crime lends itself to dispassionate, rational analysis. In the past, no issue seemed more politicized. Many local politicians won because of 30-second ads showing how tough on crime they were. Lee Atwater’s infamous Willie Horton ad for George H.W. Bush’s 1988 campaign was perhaps the nadir of American political communication until recently. Democrats also competed to be the toughest on crime and terrified voters — wrongly — with the specter of superpredators.

Creating mass incarceration 30 years ago was a bipartisan project. So it’s fitting that undoing it is as well.

One reason for bipartisanship is that the criminal justice system has affected so many people — 30 percent of American adults have a criminal record, which the F.B.I. defines as an arrest on a felony charge. “Every single American family is impacted by the broken justice system,” said Holly Harris, the executive director of Justice Action Network, which works with Republicans and Democrats at the federal and state level to reform criminal justice.

This is in large part because substance abuse now affects everyone. The crack cocaine epidemic of the 1980s and 1990s fueled mass incarceration because many white people (who made the laws) saw addicts — largely African-Americans from city neighborhoods — as criminals to be feared. Not any more. “It’s crawling across everybody’s back yard,” Ms. Harris said.

This is what sets criminal justice apart. We can’t demonize the other side, because they are us. Yes, the race and class disparities are still horrendous. But we probably wouldn’t have the First Step Act today had Jared Kushner’s father not served 14 months in federal prison beginning in 2005 for tax evasion, witness tampering and making illegal campaign donations.

The Justice Action Network is the advocacy arm of the Coalition for Public Safety, which began in 2015 to gather organizations like the American Civil Liberties Union and the N.A.A.C.P. on the left, and Right on Crime and Faith and Freedom, on the right.

This is unusual. “Lots of groups are nonpartisan, but that’s not the same as ensuring weight for progressives and conservatives,” said Inimai Chettiar, the legislative and policy director for the Network and the Coalition, both of which are primarily funded by Laura and John Arnold.

The Network forms similar bipartisan coalitions in states, and works with legislators such as Mr. Harris and Ms. Delozier. It began in Pennsylvania, Ohio and Michigan, and next year will work in 20 states. At the federal level, the Network’s advocacy was crucial to expanding the First Step Act to include sentencing reform.

The Network will only pursue a reform if its motley group of members unanimously agree. Those issues don’t include policing, guns or the death penalty — issues on which partisan divides are strong. The Network does work on reforming pretrial detention, sentencing, probation and parole, civil asset forfeiture laws, and the fines and fees charged to defendants and inmates. It also works to establish alternatives to incarceration, more humane treatment for women in prison, and a path after prison to a successful, law-abiding life.

“It was never acrimonious,” said Ms. Harris, who had been the general counsel of the Republican Party in Kentucky. “We had to build trust and understand each other’s reasons. But the real challenge was getting people to start talking. Once there was a dialogue, it was incredible how much they agreed.“All my life I’ve worked in Republican politics — that’s brutal in Kentucky,” Ms. Harris added. “We went through a really terrible governor’s race. The toxicity of the political environment was awful. I needed a change, and criminal justice reform work was going in a different direction.

“If you had told me ten years ago I’d be working hand in hand with the A.C.L.U., I would have called you crazy. But now some of those advocates are great friends and great blessings. It was attractive to me to put anger and bitterness aside and be a uniting presence rather than a dividing one. I’m a better mom and better person, and it’s helped me see the world in terms of opportunities rather than obstacles.”

Another Republican, Jenna Moll, leads the state work for the Network, while Ms. Chettiar, a Democrat who directed the justice program at the liberal Brennan Center for Justice at N.Y.U. School of Law, a liberal organization, leads the federal work.

Ms. Chettiar and Ms. Harris have become friends. Ms. Chettiar said they often discuss the many things they don’t agree on. “It’s quite interesting to be able to learn what the other side thinks, because most people don’t know that,” she said. “You misunderstand their intentions if you don’t listen to why they feel the way they do.”

As civil discourse nears a complete collapse in Congress, the people I interviewed all said that criminal justice reform is doing just fine. “We were worried when a lot of the impeachment stuff started that we would see the bipartisanship abate,” Ms. Harris said. “It hasn’t at all.”

Ms. Delozier agreed. “The news stories report on us when we’re fighting. But more and more are open to working across the aisle,” she said. The reason is simple math. “You need 102 votes,” she said.

On criminal justice reforms, the language from left and right seems to be converging. “Originally, conservatives talked about these issues in terms of public safety, recidivism reduction, curbing government spending and big government,” Ms. Harris said. (The prison system is a perfect conservative target: a hugely expensive failure of a government program that deprives people of their freedom.) “And progressives talked in terms of reducing racial disparities and increasing fairness. But I’ve watched that evolve.”

Bipartisanship is not an easy sell to constituents, Ms. Delozier said — especially overcoming mistrust between rural and urban areas. “If I talk to my folks out in central Pennsylvania, they’ll say why are you working with a Democrat? Actually, I get more questions on why I’m working for someone from Philadelphia, rather than a Democrat.

“I ask it back to them. All I hear about is the frustration we can’t work together: why are we always fighting?”

Mr. Harris said he’s been attacked on Twitter for attending a discussion with the Pennsylvania House majority leader, a Republican, at a conservative organization.

“The truth is that my constituents are trapped in the quicksand of the criminal justice system,” he said. “They don’t have time for me to wait. If that means working with the Republican Party and people I disagree with on many other things, I don’t care. I will go to the gates of hell if I have to, to pull out a positive outcome for my constituents. That’s what they voted for me to do.”

Tina Rosenberg won a Pulitzer Prize for her book “The Haunted Land: Facing Europe’s Ghosts After Communism.” She is a former editorial writer for The Times and the author, most recently, of “Join the Club: How Peer Pressure Can Transform the World” and the World War II spy story e-book “D for Deception.”

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