WASHINGTON ― With a blessing from Donald Trump ― a politician so “tough on crime” he still thinks the Central Park Five are guilty ― Congress could pass a bill before the end of the year to make the criminal justice system a little less harsh and a little less racist.

There’s just one problem: Senator Tom Cotton.

“Thousands of people will be released within weeks or months of a bill like this passing,” the Arkansas Republican told HuffPost. “I think it’s a danger to public safety and not sound policy.”

The bill is called The First Step Act. It aims to reduce recidivism and would shorten some prison sentences. Both Republicans and Democrats support the bill. The American Civil Liberties Union likes it, and so does FreedomWorks, the conservative lobbying group associated with the Tea Party movement.

But Cotton is doing everything he can to sour Republicans on the legislation. He railed against the bill during a lively Tuesday lunch meeting with his Republican colleagues, warning them they would be blamed if any recently released prisoner commits a new crime.

“He was the guy who was most sharply against the bill,” Sen. Lindsey Graham (R-S.C.) told HuffPost. “He’s saying, ‘Someone’s going to get out; we’re all going to lose our seats’.”

And since Senate Majority Leader Mitch McConnell (R-Ky.) has said he doesn’t want to put the bill up for a vote if it divides his party, Cotton could get his way.

“It’s too bad that I agree with Cotton 90 percent of the time, and on something like this that I think is very strong on law enforcement [we don’t],” Senate Judiciary Committee Chairman Chuck Grassley (R-Iowa), a major proponent of the bill, said Tuesday.

“We’ve just gotta keep working, and we’re going to have to overcome Cotton’s opposition,” he added.

McConnell has said the Senate might not have time to consider the bill before it adjourns for the year, especially with the looming lapse in government funding in the next few weeks and several other must-pass items on the agenda. Opponents like Cotton are likely to drag out the process on the floor as much as possible ― which could eat up a week or more.

Proponents of the effort, however, fear that if the Senate doesn’t take up the bill in the lame-duck Congress, its chances of passage next year may be substantially harder with Democrats in control of the House. Newly elected Democratic members in the House may add more liberal provisions that could bog down the bill in the Senate, for example.

“If it doesn’t happen this year, it’s probably never going to happen,” Graham told reporters on Tuesday.

Sen. Tim Scott (R-S.C.), another supporter of the bill, estimated on Tuesday that 21 Republicans are firmly on board with the measure. Another five GOP senators, he said, are “soft” yeses. The bill has 11 Democratic co-sponsors.

Federal inmates accounted for fewer than 200,000 of the more than two million Americans locked up in prisons and jails in 2016, according to the latest numbers from the Bureau of Justice Statistics. The federal prison population skyrocketed from just 25,000 in the early 1980s thanks to new mandatory minimum sentences and the elimination of parole. In recent years the number of inmates has gradually declined.

One of the most notorious mandatory minimums of the 1980s established a five-year sentence for offenses involving 500 grams of cocaine or just 5 grams of crack cocaine ― meaning the penalty for crack was 100 times harsher than the penalty for regular powder cocaine, even though crack is nowhere near 100 times more harmful. The harsher penalty overwhelmingly fell on African-Americans, who comprise 38 percent of federal prisoners but only 13 percent of the overall U.S. population.

ASSOCIATED PRESS Sen. Cotton is doing everything he can to sour Republicans on the legislation.

Congress passed a law in 2010 that reduced penalties for crack offenses. Instead of being 100 times harsher than the sentences for regular cocaine crimes, the compromise law made the penalties only 18 times harsher. But lawmakers elected not to make the change retroactive. As a result, more than 2,000 federal crack offenders remain in prison today even though they’d be free if they’d been sentenced under current law.

The First Step Act would give such offenders a chance to petition the courts for a review of their case, which Tom Cotton thinks is awful.

“There was long, careful debate about those provisions. Retroactivity was one specific part of that debate,″ Cotton said. “That was the compromise that was struck in 2010. I think it’s a reasonable compromise.”

The version of the bill that passed the House earlier this year, by a vote of 360 to 59, did not include the retroactive crack provision. The lack of sentencing reform was one of the reasons that more than 100 liberal policy groups signed a letter of opposition by the Leadership Conference on Civil and Human Rights. The core of the legislation is a “risk and needs assessment program” that critics say would give the government too much leeway to decide which prisoners are at the lowest risk of committing crimes in the future if they are released early.

The latest Senate version of the bill, which Grassley and several Democrats released last week, added the crack provision and three other reforms to mandatory minimums that wouldn’t apply retroactively. The Leadership Conference hasn’t signaled support or opposition to the new bill, but the changes did win over the American Civil Liberties Union.

“It is the thing that tipped us over the scale to support this,” the ACLU’s Jesselyn McCurdy said.

Cotton helped spoil criminal justice reform legislation in 2016 and has an extraordinary willingness to make a stink over things he doesn’t like. In 2015 he wrote an unusual “Open Letter to the Leaders of the Islamic Republic of Iran” warning them that a future president and Congress could abdicate a nuclear agreement the Barack Obama administration and other countries had struck with Iran. That same year, he blocked an ambassador nomination simply to spite the former president (something he later said he somewhat regretted). He’s said he goes for long runs in the morning so that he can eat birthday cake almost every day.

Trump had essentially been fooled into supporting the prison legislation, Cotton said. The White House trumpeted the act in a release the day before the Senate unveiled its latest version.

“The bill was only released Friday before Thanksgiving after the president endorsed, in the abstract, the concept of prison reform,” Cotton said. “What started as an effort at prison reform to help prisoners get back on their feet once they leave prison, once they’ve paid their debt to society, has turned into a sentencing leniency bill.”