WASHINGTON — These days the most optimistic people in Washington deal with a dark topic: overhauling the nation's criminal justice system.

The biggest reason for the optimism is, after decades of tough-on-crime politicians from both parties, the groups behind the push for new prison policies are unusually bipartisan.

Not that they'll admit to that just yet — there's still a lot of wariness, especially on the conservative side. But behind the caution is a real sense of movement with ideologically divergent politicians like Sens. Rand Paul and Patrick Leahy working together on legislation and groups like the conservative Right on Crime quietly taking meetings with the NAACP and ACLU on the issue of criminal justice.

"I've been working this field since 1990 and this is certainly the most hopeful time I've seen in that 25-year period," said David Fathi, ACLU National Prison Project director. "There is an openness to fundamentally rethinking our approach to crime and deviant behavior in a way that I've never seen before."

Across the country, bipartisan activists are targeting almost every area of the criminal justice system. In states like California, conservatives eager to save money have advocated for release programs in states that would place more convicts in probation programs and pursue alternative punishment options to keep nonviolent offenders out of prison in the first place.

Additional changes to the justice system favored by some on the right like the end of mandatory minimum sentences represent a big change to conservative rhetoric on crime — one that progressives have been waiting to hear for years.

In fact, these days the ACLU and Right on Crime basically speak with one voice on this topic: Both groups are deeply rooted in their respective ideological political sides, but they both want to see the way prisons are run change. ACLU (and other liberal groups involved in efforts to change criminal justice policy) say they've had productive conversations with Right On Crime, especially on the state level where advocates have effectively pushed for legislation in such unlikely places as Texas, where the conservative group is based.

But Vikrant Reddy, a senior policy analyst at Texas-based Right on Crime, steered clear of any suggestion his group works closely with progressive activists.

"Real coordination between the two sides isn't really happening in the way people think it is," he said. Reddy said that there have been "incidental" meetings between conservatives and progressives on prison policy and even some relationships formed as leaders keep appearing on the same legislative panels together. But no one is giving in to form a unified theory of changing the criminal justice system, he said.

"I don't think people on the right are saying, 'Let's compromise in this way so we can get a bill passed' or the left is saying, 'Let's compromise in that way so we can get a bill passed,'" Reddy said. "Both sides on a really fundamental level are pushing what they feel is good policy."

Reddy, trying to sell a vision of criminal justice that would see less people go to jail to a conservative crowd, said embracing the left isn't the best way to go about that.

"I don't think it helps to walk into the Heritage Foundation and say, 'The ACLU thinks this is a great idea,'" he said. "But nor do I think it helps to walk into the ACLU and say 'The Heritage Foundation thinks this is a great idea.'"

Meanwhile, progressives — who have been waiting for at least a generation to see the political conversation move in the direction it seems to be moving — are predictably thrilled to have conservatives on board.

"We absolutely are talking to them and collaborating with them on issues where we agree," Fathi said.

And as for the idea that there's a danger for the ACLU in working with conservatives, Fathi disagreed. "I can only speak for the ACLU and I can truthfully say I have never heard that objection," he said. "The ACLU is an organization of principles and if someone agrees with us, we will work with them on those issues."

The last week of February offers a good case study for why activists are more hopeful than ever. On that Monday, the Justice Department sent what Fathi called the first federal reprimand to a state government over its use of solitary confinement. The scathing Justice report on Pennsylvania's prison system found it "uses solitary confinement in ways that violate the rights of prisoners with [serious mental illness/intellectual disabilities]."

The Federal Bureau of Prisons has ordered an outside review of solitary confinement practices — a review that could lead to sweeping changes to the way federal prisons use isolation.

The next day, the Senate Judiciary Committee devoted a hearing to solitary confinement. On the panel of experts calling for reform was Marc Levin, policy director at Right on Crime.

On Thursday, President Obama prominently mentioned criminal justice in high-profile remarks on the "My Brother's Keeper" initiative aimed at improving opportunities for minority boys.

Activists feel like it's a big moment in Washington — but they believe there's some sustaining momentum in Congress as well.

Reddy and his colleagues at Right on Crime aren't the only Republican-leaning advocates out there pushing for major changes to the prison system these days. Paul has become something of a poster-child for a new conservative focus on ending mandatory minimum sentences and restoring voting rights for felons. Though he's a vociferous critic of the president, Paul hasn't had a problem reaching out to leaders in the Obama administration who are also talking about changing the criminal justice system. He and other Republicans have met privately with Attorney General Eric Holder about efforts to change sentencing laws that result in mandatory minimum sentences.

The rise of libertarians and progressives has begun to chip away at decades of tough-on-crime Republicans — and many Democrats — who favored a position often summarized as "throw away the key." Progressives attribute their changing fortunes to housing bubble bursting on Wall Street.

"I think the fiscal crisis has been a real opening," Fathi said. "The fiscal crisis has forced many states, probably most states, to take a hard look at what they're spending on crime control policy. Once you start asking questions, I think it becomes easier to continue that process and just become more critical and more skeptical about the recovered wisdom."

Reddy said the Republican focus on core principles helped create the drive for changes to the criminal justice system.

"On our side, we are staying true to our philosophical roots: limited government, and a real rigorous focus on spending and personal liberty and personal responsibility," he said. "All those things are consistent with prison reform."

Whatever the driving force, it seems that so far, the budding prison reform movement has avoided a breakdown over who deserves the credit for its success — or who should take the blame for a potential political liability in an election year. For now, the debate remains largely in the Senate and among White House leaders. Should things move to the less predictable House, where things end up is anybody's guess. But there's an optimism in the talk from advocates you just don't hear from just about anybody else in Washington these days.

"There's a bill to reform federal mandatory minimums that is co-authored by both Rand Paul and Patrick Leahy," Reddy said. "You just can't conceive of people with more different world views in Washington, D.C."

"Whenever you get an agreement between people like that, you would think that there is a real opportunity for the bill to move forward. So I'm optimistic. I really am."