WASHINGTON

President Trump’s boisterous and often denigrating political rhetoric during most of the 2018 midterm campaign season and his post-election assault on the federal court in California may have overshadowed his positive take on federal prison sentencing.

President Trump announced just after the Nov. 6 elections that he is fully endorsing a bipartisan bill in the works in the U.S. Senate that makes sweeping changes in the controversial federal prison sentencing laws related to convictions for illegal drugs.

The compromise bill, which reportedly is in its final stages, would mark the first sweeping reform of the controversial sentencing law in more than a decade.

Observers said the compromise restores the authority of federal judges to exercise discretion in setting sentences in most drug convictions. It reduces the mandatory minimum prison time required in most drugs convictions, they said. It also closes the sentencing gap between powder and crack cocaine convictions and makes portions of the law retroactive to cover past convictions, said people knowledgeable of various versions of the proposal being finished by GOP Sen. Chuck Grassley of Iowa and Democratic Sen. Dick Durbin of Illinois.

The U.S. House of Representatives passed a narrowly focused “First Step “ bill in May aimed at boosting rehabilitation programs for federal prisoners. But the overhauled Senate version of the bill, championed by Sens. Grassley and Durbin, is far more reaching, according to legislative watchdogs on Capitol Hill.

Third District Congressman Robert C. “Bobby” Scott of Virginia has spent more than a decade working with a bipartisan group of House colleagues to craft legislation reversing mandatory minimum sentencing. He voted for the “First Step” bill in the House earlier this year. But he is withholding comment on the newest development with the president, an aide said, pending more details.

A final version of the Senate bill has not been circulated and there is no certainty it will pass the Senate or the House when completed.

“I’m waiting with a pen,” to sign a compromise bipartisan federal sentencing reform bill, President Trump said in his brief announcement. “It’s the right thing to do.”

Sen. Grassley, who counted himself in the 1990s among staunch proponents of harsh prison sentences for convicted drug offenders, today views himself as a sound advocate for toning down the strategy.

Among the last law-and-order leaders blocking sentencing reform was former Attorney General Jeff Sessions of Alabama. Just after the midterm elections, Mr. Sessions, a former U.S. senator, announced he was resigning, at President Trump’s request, as U.S. attorney general. Mr. Sessions had used his post in the Trump administration to actively call for tougher prison time for federal crimes, especially for people convicted of illegal drug offenses.

Observers said Mr. Sessions’ departure cleared the runway for sentencing reform to arrive sooner and hopefully land smoothly.

People who have followed sentencing reform work for several decades and from various points of view hailed President Trump’s declaration, while cautioning that it’s still too soon to toast a victory.

NAACP Washington Bureau Director Hilary Shelton echoed similar optimism, hastening to add the final Senate compromise is still in the mill.

“It’s great to see attention brought to a bill much broader,” said Mr. Shelton, noting the Senate compromise deals with sentencing reform issues and topics beyond prison walls.

There is guarded optimism in Richmond, where the sentencing reform movement got an added burst of steam in the early 1990s when citizens and lawmakers rallied around efforts to have hometown girl and former Hampton University student Kemba Smith freed from a 24½-year mandatory minimum federal prison sentence despite being a first-time, nonviolent drug offender.

“I think overall, it could be a good thing,” said the now-Ms. Smith-Pradia, who was freed from prison in 2000, married, had a second child, earned a degree from Virginia Union University and started a foundation to advocate on behalf of certain social issues.

Ms. Smith-Pradia, who had served 6½ years in federal prison when President Clinton commuted her sentence to time served, has been in White House discussions about sentencing reform during the Obama years and President Trump’s tenure.

In a brief telephone interview, Ms. Smith-Pradia describes herself as guardedly optimistic about President Trump’s endorsement of the sentencing reform plan. She said she needs to learn more details of the proposed compromise.