(CNN) - Senate Majority Leader Mitch McConnell announced Tuesday that the Senate will take up a significant criminal justice reform bill this month to overhaul the nation's prison and sentencing laws, paving the way for its passage before the end of the year.
White House officials and outside advisers who have been championing the First Step Act are celebrating McConnell's decision. Members of McConnell's own caucus -- most vocally Arkansas Sen. Tom Cotton -- came out strongly against the legislation, opposition that seemed like it could sideline the legislation for the foreseeable future without assistance from McConnell.
The legislation, known as the First Step Act, would allow some current and future prisoners to get out earlier, and rehabilitate into society through halfway houses, home confinement or other supervision, by reducing drug-related mandatory sentences and making more offenders eligible for early release. For a prisoner to reduce his or her sentence, they'd need to be determined by the Bureau of Prisons as a "low risk" for recidivism and earn credits through certain activities and programs.
For weeks, it appeared that a core of conservatives in the Senate who loudly opposed the bill would divide the Republican conference and prevent it from coming to the floor. While their opposition hasn't ceased -- some are now calling for an intense debate on the floor -- it appears their voices are outnumbered.
McConnell, who has not publicly stated his position on the bill, said he would bring up the legislation "as early as the end of this week" but warned that senators would have to work between Christmas and New Years unless opponents of the bill decide not to filibuster it.
"Members should either prepare to cooperate and work together -- or prepare for a very, very long month," said McConnell.
Trump, House supporters rejoice
White House officials, House Speaker Paul Ryan, a large crew of Republican and Democratic senators and outside groups who have been championing the First Step Act are now celebrating McConnell's decision to bring the bill to the floor.
"As the speaker has said, the House stands ready to act on the revised Senate criminal justice reform bill," said Ryan spokesperson AshLee Strong.
They are confident the bill will pass when it comes to the floor and said a combination of grassroots pressure, phone calls from Trump to McConnell in recent weeks and some changes to the bill were critical to McConnell agreeing to bring the bill to a vote.
Sen. Lindsey Graham, Republican of South Carolina, estimated on Tuesday that the bill has the support of 80 senators — well over the number necessary to pass.
"These are long overdue reforms and it's worth us staying in session to get done if necessary," Graham said.
One of the key changes made to get additional Republican votes -- namely Republican Sens. Ted Cruz of Texas and Sen. David Perdue of Georgia -- were to the so-called safety valve provision. The change will give judges slightly less discretion about whom they can exclude from mandatory minimum sentences, a person familiar with the matters said.
In a sign the bill would pass, Sen. John Cornyn, the GOP whip, said Tuesday he would support the bill after some changes requested by the law enforcement community were included in it.
Jared Kushner, Trump's son-in-law, played a key role in moving the bill forward. Kushner took to Sean Hannity's Fox News program to tout the bill Monday evening and was on the phone with Graham on Tuesday morning continuing to push for it.
"If this thing gets done, and I hope it will, he deserves the lion's share of credit," Graham said.
Kushner's interest in the criminal justice reform effort stems from his father, Charles Kushner, who was sentenced to two years in prison after being convicted in 2005 of witness tampering, illegal campaign contributions and tax evasion, according to Graham.
"He explains his father's situation as opening his eyes to it," Graham said.
Cotton leads opposition
Cotton criticized the bill in a statement Tuesday, though he acknowledged some changes were made to improve the proposal.
"For months I've said the First Step Act allows violent felons and sex offenders to be released early. I'm pleased the drafters have finally acknowledged that reality and made changes to address some of the specific issues I pointed out," Cotton said. "Unfortunately, the bill still has major problems and allows early release for many categories of serious, violent criminals."
Cotton was sharper in his dismissal when he spoke to reporters on Capitol Hill.
"I don't think the Senate should vote to let carjackers and bank robbers out of prison," Cotton said. "Maybe other senators do and that's their prerogative. But I will have lots of amendments to offer and they can make their choices."
But after a unusual coalition of liberal and conservative groups came together to push it through Congress, Cotton's view is appears to be a minority one in the Senate.
Jessica Jackson Sloan, the founder of #cut50 who has worked closely with the White House to craft the First Step Act, said Trump was on the phone with multiple senators over the weekend to discuss the bill. She said Trump and McConnell also spoke over the weekend.
"This was a full court press," said Jackson Sloan.
"When you have everybody from Ted Cruz to Cory Booker to Nancy Pelosi to Donald Trump -- that's pretty incredible," she added. "You know that something real is going on here."
This story has been updated with additional developments.
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