Read: Sentencing: the judge’s problem

The bill would let some federal inmates participating in “evidence-based recidivism reduction programs” earn credit to leave prison more quickly; the sentencing reform added in the Senate trims future mandatory minimum sentences for drug crimes and lets prisoners sentenced under the old crack-cocaine rules petition for a reduced sentence in line with the recent reforms.

On Friday, Trump tweeted that Senate Majority Leader Mitch McConnell should allow a vote on the “extremely popular” package.

Top GOP senators predict that it would get 25 or 30 Republican votes in their chamber and pass with a bipartisan supermajority. But now McConnell has refused to bring it up in the current lame-duck session, and supporters fear for the bill’s future in next year’s divided Congress.

“I’ve got this much time,” McConnell said this week at a Wall Street Journal event, holding his hands close together. He said such a bill requires a week or ten days to consider, while there are only two weeks left before the planned holiday recess and budget bills that must be passed before then; advocates argue that it would only take a few days, with a cloture vote capping debate at 30 hours. McConnell acknowledged support on both sides of the aisle but called the legislation “extremely divisive inside the Senate Republican conference,” with more members undecided or opposed than in favor.

“That’s his calling card, protecting his conference,” said Kevin Ring, the president of Families Against Mandatory Minimums and a leading reform advocate who spent more than a year in federal prison for his role in the Jack Abramoff lobbying scandal. While past majority leaders like Lyndon Johnson might have strong-armed their members, McConnell waits for near-unanimity among Senate Republicans. “I think he’s not just looking for 60 votes,” said Brett Tolman, the former top federal prosecutor in Utah who also worked as a GOP Senate staffer and now advocates for criminal-justice reform. “He’s looking for a majority of Republicans.” That seemed more likely as Senator Ted Cruz, a former skeptic of the bill, came out in favor of it Friday afternoon after the sponsors accepted his minor amendments; his support could lead more conservative Republicans to join him.

Above all, Ring said in an interview last week, McConnell wants to avoid GOP infighting and protect his senators in their reelection fights. There’s the specter of anti-reform senators like Tom Cotton of Arkansas calling other Republicans “soft on crime,” despite endorsements from Trump and law-enforcement organizations like the Fraternal Order of Police. Cotton charges that if the bill becomes law, “thousands of federal offenders, including violent felons and sex offenders, will be released earlier than they would be under current law.” Supporters say that Cotton is misleading the public by ignoring the required risk assessment that would screen out high-risk inmates, even if the law does not exclude their crimes specifically.