Launching a trans-partisan effort may seem odd in this polarized political climate, but it has a certain logic in the context of criminal justice. Mass incarceration, after all, was a triumph of bipartisanship. Republican contributions often receive the most attention. Ronald Reagan oversaw the dramatic expansion of the war on drugs. Willie Horton's impact in the 1988 presidential election helped deliver George H.W. Bush the presidency while suffocating criminal-justice reforms in Massachusetts and elsewhere. Conservative states like Texas, Louisiana, and Alabama saw the fastest rise in incarceration rates.

But many prominent Democrats also contributed to the carceral state’s growth. Senator Ted Kennedy championed the use of mandatory sentencing guidelines and worked with Strom Thurmond to secure the Sentencing Reform Act’s passage in 1984. Bill Clinton's 1994 omnibus crime bill, which passed Congress with the strong support of Joe Biden, Kennedy, and other major Democratic lawmakers, added $9.7 billion in new funding for prisons. As the incarceration rate jumped during the 1990s, Congress passed and Clinton signed the Prison Litigation Reform Act in 1996. The law added new barriers to prisoner lawsuits that challenged their treatment and conditions.

Liberal governors and state legislators also played their part. New York Governor Mario Cuomo, a Democratic standard-bearer in the 1980s, built dozens of new prisons during his twelve-year tenure to fill the demand created by the state’s Rockefeller drug laws. To avoid raising taxes, Cuomo turned to the state’s Urban Development Corporation to finance new prison construction. The corporation was originally designed to fund housing projects for New York’s poorest. In a dystopian way, it succeeded.

What changed the bipartisan consensus? Perhaps the most important development is the sharp decline in crime since the turbulence of the early 1990s. New research shows that incarceration bore little to no responsibility for the decline in crime, although the exact causal mechanisms are still heavily debated. Another major factor was the Great Recession, which forced states and the federal government to reckon with the high costs of large-scale imprisonment. New York City spent nearly $100,000 per inmate at Rikers Island in 2014; a year's tuition at New York University costs roughly $46,000 per student by comparison. Finally, scholars like Marc Mauer and Michelle Alexander re-framed how Americans view crime, race, and poverty in the public sphere. Like "climate change" or "immigration reform," the phrase "mass incarceration" brings semantic order to a disordered set of interconnected concepts.

These shifts blunted the "tough-on-crime" mentality that had suffused American political discourse for decades. Even the nation's highest law-enforcement official embraced the change. "Today, a vicious cycle of poverty, criminality, and incarceration traps too many Americans and weakens too many communities," said Attorney General Eric Holder in a 2013 speech to the American Bar Association. "And many aspects of our criminal justice system may actually exacerbate these problems, rather than alleviate them." Democratic stalwarts like Patrick Leahy and Cory Booker and conservative Republicans like Rand Paul and Ted Cruz now plan to propose sentencing reforms that would have been considered unthinkable a decade ago. President Obama met with some of the Smarter Sentencing Act's sponsors on Wednesday.