In a 1989 speech, Sen. Joe Biden blasted President George H.W. Bush, saying he wasn't doing enough to put the "violent thugs" responsible for the nation's spiraling crime rate behind bars. During that time, Biden sponsored bill after bill that would do just that, helping to usher in an era of mass incarceration that would define criminal justice policy for decades and fall heavily on Black and Brown communities. Now, as president-elect, Biden has promised a remarkable turn: changes that some activists view as among the most ambitious of any recent president-elect aimed at undoing the jail and prison buildup he supported three decades ago. Biden even went so far as to tell a voter during the primary campaign that his administration would cut the nation's prison population by more than 50%, something few experts consider realistic in just four years. "Let us vow to make this, at last, an era of action to reverse systemic racism with long-overdue and concrete changes," Biden said in a speech this summer that reflected his evolution. Biden plans to attack mass incarceration on multiple fronts, but he faces head winds from lingering distrust on the left from his earlier incarnation as a tough-on-crime politician. Biden's transition team did not offer comment for this article. "On paper, it's great," Kevin Ring, president of Families Against Mandatory Minimums, said of Biden's agenda. "But, I will say, there's a lot of skepticism from people about him taking down the house he helped build. . . . I take him at his word. . . . I think the country's moved and I think a lot of people have." Ring said Biden could allay fears on the left by moving quickly and boldly. A great first step would be to continue to close the sentencing disparity between crack and powder cocaine that has resulted in harsher sentences disproportionately affecting Black defendants, he said. The Obama administration narrowed the gap. The proposal is just one that Biden has put forward to cut mass incarceration. A cornerstone is a call for Congress to send him the Safe, Accountable, Fair and Effective Justice Act, a wide-ranging bill that aims to cut incarceration by tackling everything from sentencing on the front end to prison release policies on the back. Biden also wants to establish a $20 billion grant program that would incentivize states to shift from incarcerating offenders to addressing the underlying causes of crime through funding for counseling for mental health, addiction and child abuse, as well as a range of social services and early-childhood education. Biden says he will work to repeal federal mandatory minimum sentences, end cash bail, stop the use of solitary confinement, suspend sentences for drug use and instead divert defendants into drug courts, expand alternatives to detention, knock down barriers to reentry, and liberally use clemency to secure the release of inmates facing overly long sentences for drug and nonviolent offenses. He also promises to end the federal government's use of private prisons and condition federal grants on the adequate provision of health care for female prisoners. In addition, he said he will seek to cut the youth incarceration rate by pushing states to adopt alternatives to imprisonment for young people. One area that is not addressed in Biden's platform on prison policy, but will be a major issue for his administration, is the massive outbreaks of the coronavirus in prisons and jails. Activists said they expect the Biden administration to put forward a plan at some point. One in 5 of the nation's prisoners has been infected with the coronavirus and more than 1,700 have died of covid-19, according to data from the Associated Press and the Marshall Project. Biden can implement some of his agenda through executive orders and Justice Department policy, but a good chunk rests on congressional approval, which Ring said will be Biden's biggest challenge in a Washington paralyzed by partisanship. Some of the loudest voices in the Republican Party - who may seek the presidency in 2024 - have been cool to proposed changes. They include Sens. Tom Cotton (Ark.) and Josh Hawley (Mo.). Still, one of the few examples of cooperation across the aisle in recent years was the bipartisan push for the First Step Act, which was signed by President Donald Trump and has reduced tough sentences for thousands of federal inmates. Another challenge for Biden is that a president has only limited influence over state prisons and jails, where more than 90% of inmates are housed. There are 153,000 inmates in federal custody, according to the Bureau of Prisons, while the Prison Policy Initiative reports that there are more than 2 million in state facilities. Any meaningful effort to reduce mass incarceration will have to spur states to make changes as well. Lauren-Brooke Eisen, director of the Justice Program at the Brennan Center for Justice, said Biden can use his bully pulpit as president and the federal government's purse strings to foster changes. "Through funding mechanisms, the Biden-Harris administration can do a lot," she said. Read More Anti-tax surge comes to Wyoming amid budget crises Proposal to build gas terminal on Delaware River could test Biden administration USPS delays are threatening small-town newspapers. So is a postage price increase. Subscribe to The Post Most newsletter for the most important and interesting stories from The Washington Post.