WASHINGTON >> President Donald Trump threw his support behind a substantial revision of the nation’s prison and sentencing laws today, opening a potential path to enacting the most significant changes to the criminal justice system in a generation.

The tentative legislative package, developed by a bipartisan group of senators and called the First Step Act, builds on a prison overhaul bill already passed overwhelmingly by the House by adding changes that would begin to unwind some of the tough-on-crime federal policies of the 1980s and 1990s that incarcerated African-American offenders at much higher rates than white offenders.

Combining new funding for anti-recidivism programs, the expansion of early-release credits for prisoners and the reduction of certain mandatory minimum sentences, the compromise bill would help shape the experiences of tens of thousands of current inmates and future offenders.

“In many respects, we’re getting very much tougher on the truly bad criminals — of which, unfortunately, there are many,” said Trump, flanked by Republican lawmakers and law enforcement officials. “But we’re treating people differently for different crimes. Some people got caught up in situations that were very bad.”

He urged Congress to promptly send him a final bill to sign. “It’s the right thing to do,” Trump added.

Trump’s support could give political cover to Republicans wary of reducing some hard-line sentencing rules for drug and other offenses, and enable the legislation’s sponsors to assemble a coalition of moderate Republicans and Democrats in time to move a bill before the year’s end — and before the new, divided Congress is seated.

The changes have attracted a broad and unusual range of supporters, including the billionaire brothers Charles G. and David H. Koch on the right and the American Civil Liberties Union on the left. Conservatives see an opportunity to begin to cut into the high costs of the nation’s growing prison population. Liberals have long opposed the current sentencing laws for what they see as having unfairly incarcerated a generation of young men, particularly African-American men, for drug and other nonviolent offenses.

But even with Trump on board, proponents must now compete with a rapidly closing window to move a complicated bill with broad implications for the criminal justice system. As of this morning, many senators had not yet even seen a draft of the bill, and some conservatives were thought to be firmly against it. Liberals have their own reasons to be disappointed because most of the proposed sentencing changes have not been made retroactive, drastically limiting their effect.

“We don’t have a whole lot of time left,” Sen. Mitch McConnell, R-Ky., the Senate majority leader, told reporters today. McConnell had previously pledged to take up the bill if it had at least 60 senators supporting it. But he added that given the time pressures, he would also have to “see how it stacks up against our other priorities going into the end of our session.”

Jared Kushner, the president’s son-in-law and the leading advocate of the criminal justice package within the White House, presented the tentative deal to Trump on Tuesday. The president was initially noncommittal but later offered a firmer yes, according to administration and congressional officials briefed on the meeting.

Trump’s support today breathed unexpected life into a legislative effort that had more than once appeared to be dead. Democratic and Republican lawmakers first mounted a serious and more expansive criminal justice overhaul in 2015. They had the backing of President Barack Obama, House Speaker Paul Ryan and a cross section of lawmakers in both parties and appeared destined for success.

Two of the long-sought changes included in the legislation are shortening mandatory minimum sentences for some nonviolent drug offenses and changing the “three strikes” penalty to 25 years from life in prison. Judges would also have greater freedom to use so-called safety valves to sidestep mandatory minimums in some cases. And the bill would clarify that the stacking mechanism making it a federal crime to possess a firearm while committing another crime, like a drug offense, should apply only to individuals who have previously been convicted.

It would also extend retroactively a reduction in the sentencing disparity between crack and powder cocaine signed into law in 2010, which could affect thousands of drug offenders serving lengthy sentences for crack-cocaine offenses, which were dealt with far more harshly than the same crimes involving powder cocaine. That disparity hit black Americans hard while letting many white drug dealers off with lighter punishments.

The Fraternal Order of Police, the country’s largest police organization, said last Friday that it would support the bill, and the National Sheriffs’ Association appeared to have dropped some previous objections after exceptions were made to block certain fentanyl offenders from eligibility for “good-time credits” included in the prison overhaul portion of the bill.

But powerful pockets of opposition remain among some law enforcement officials and conservative lawmakers — like Sen. Tom Cotton, R-Ark. — who argue that sentencing changes like those proposed pose a risk to public safety. However, they lost a powerful ally within the administration when Trump fired his attorney general, Jeff Sessions, last week. Sessions’ temporary replacement, Matthew Whitaker, has signaled that he is more open to the changes.

Trump himself is leery of appearing weak on crime, and he has been susceptible to arguments from opponents of a sentencing overhaul that endorsing one could arm his critics. Still, Kushner has pressed the issue for months, and some of the president’s advisers say they think the effort could help improve his anemic standing with African-American voters, even if only marginally.

In his remarks today, Trump tried to address both points, saying that the legislation would be tougher on hardened criminals. But in a reference to the tough-on-crime policies embraced by President Bill Clinton, Trump also said that the legislation would begin to roll back portions of the “Clinton crime bill” that had a “very disproportionate and very unfair” effect on black Americans.

© 2018 The New York Times Company