The Senate is poised to vote on a bipartisan criminal justice bill as soon as this week, the culmination of behind-the-scenes negotiations and a public campaign by lawmakers, the White House and advocates to press Majority Leader Mitch McConnell to bring it to the floor this year. But that does not mean the debate will be free of drama. 

McConnell announced Tuesday that the revised bill would be put on the floor agenda this month “following improvements to the legislation that [have] been secured by several members.” That ended weeks of uncertainty about whether the Senate would have a chance to vote on prison and sentencing changes that would be the first in a generation and could become a signature accomplishment right before the end of the 115th Congress.

“I think we’ll see a number of Republicans now come on board supporting this bill as amended,” said Majority Whip John Cornyn of Texas, who announced his support Tuesday morning, citing three changes to the bill. “In fact, people now know we’re going to vote on it, it’s going to cause people to have to make decisions. But I’m pretty optimistic.”

The bill still faces a crowded Senate to-do list and some opposition, including a suggestion from Arkansas Republican Sen. Tom Cotton that he might stand in the way. As a result, McConnell warned that voting on the criminal justice bill means members should be prepared to work between Christmas and New Year’s Day “unless we approach all this work in a highly collaborative, productive way.”

A floor vote on the bill didn’t seem likely after the midterm elections in November. McConnell suggested that there wasn’t enough time in the lame duck session to spend floor hours on the criminal justice bill, especially because the Republican conference was divided.

Then, Sen. Charles E. Grassley, the Iowa Republican who championed a compromise bill for years as the chairman of the Senate Judiciary Committee, leaned on his track record of processing judicial nominations and publicly urged McConnell to set up a vote.

President Donald Trump backed the bill and tweeted Dec. 7, “Go for it Mitch!” The president followed that up on Tuesday with a tweet thanking McConnell for bringing up the measure. “It brings much needed hope to many families during the Holiday Season,” he tweeted. Jared Kushner, Trump’s son-in-law and senior adviser, went on Fox News on Monday night to talk it up.

McConnell was concerned about the time it would take on the floor, but “he obviously is now doing what the president asked him to do, and I think we got the bill in a better place that makes it more likely we can pass it,” Cornyn said.

Sen. Ted Cruz announced his support for the bill last week after colleagues backing the bill agreed to adopt his amendment that the Senate Judiciary Committee had earlier rejected when it considered the bill.

The Texas Republican said the amendment excludes violent offenders from being released early, and resolves his concerns. “With these changes, this bill gives non-violent offenders a better chance at rejoining society while keeping violent offenders behind bars,” Cruz said.

Georgia Republican Sen. David Perdue announced his support Monday night and said he had secured two changes, including one that removes the ability of judges to unilaterally make offenders with serious crimes eligible for reduced sentences.

The Senate Judiciary Committee lists 36 authors and co-sponsors for the legislation, among them Republicans, Democrats and independents. Dozens of advocacy groups from across the political spectrum back the effort.

The bill aims to lower the number of federal inmates through changes in some sentencing laws and through more help for prisoners returning to society so they don’t commit new crimes and go back to prison.

Cotton said he plans to offer “lots” of amendments “that will protect the public from the serious violent felons that will be released” early from prison.

“How about we start with not letting carjackers get released early from prison,” Cotton said.

“When you release thousands of serious and violent felons within just weeks or months, it’s an almost mathematical certainty that one of them will commit a terrible crime,” Cotton said. “Anyone who votes for this bill will have to answer for that crime.”

Asked about Cotton’s latest comments, Grassley suggested his colleague was making a reference to the infamous Willie Horton campaign ads from 1988 used to criticize the Democratic presidential candidate, Massachusetts Gov. Michael Dukakis, for his support for prison furlough programs. Horton raped a woman and assaulted her boyfriend while on a release. The ad has become a notorious example of using race-baiting in a political campaign. 

“It sounds to me like he wants to teach us a lesson from the 1988 … George H.W. Bush campaign,” Grassley said.

When asked if he would force the Senate to be in session between Christmas and New Year’s, Cotton replied only: “Merry Christmas.”

Niels Lesniewski and John T. Bennett contributed to this report.