Supporters of the legislation, which includes anti-recidivism programs, and the expansion of early release credits and sentencing changes, worry that Mr. McConnell is being a less-than-neutral arbiter. They believe that if consideration slips into January, when Democrats who favor more expansive sentencing changes take control of the House, the current compromise could collapse.
Like earlier efforts, the bill counts an unorthodox array of backers, including liberal groups like the American Civil Liberties Union; FreedomWorks, an influential conservative advocacy group; and the Fraternal Order of Police. But pockets of conservative opposition run deep, dividing Republicans in the Senate — a dynamic Mr. McConnell typically prefers to avoid.
The divisions were on display on Thursday.
At the Senate Republicans’ weekly caucus luncheon at the Capitol, Mr. McConnell acknowledged that the changes had influential supporters who had worked hard on the issue, but also invited two of its chief critics, Senators Tom Cotton of Arkansas and John Kennedy of Louisiana, to deliver remarks, two Republican congressional officials said.
Mr. Cotton, who has been perhaps the loudest critic of the bill’s sentencing changes in the Senate, urged colleagues to slow down the process, saying that the bill’s impact and implications were too expensive to push through without hearings, according to another official familiar with his remarks. He stressed opposition by some law enforcement groups and warned that a draft version of the bill he had seen would lead to the immediate release of thousands of felons onto the streets.
Senator Mike Lee, a Utah Republican who helped write the legislation, pushed back against Mr. Cotton’s characterization. So did Senator Charles E. Grassley, the Iowa Republican who is chairman of the Judiciary Committee and led the compromise effort. Mr. Grassley said that Mr. Cotton’s remarks made him sound like “some sort of pinko commie.”
Mr. Cotton’s office also circulated a letter from groups representing elected sheriffs raising objections to the bill. Without changes, it said, the “legislation creates a high-risk path for dangerous criminals with gun crime histories to early release from prison.” Mr. Cotton also wrote an op-ed in USA Today in which he called the legislation “a misguided effort to let serious felons out of prison.”
The legislation’s advocates caught a break last week when Mr. Trump fired his attorney general, Jeff Sessions, who had been one of the bill’s most vocal opponents within the administration and before that as a senator from Alabama.