Senate Majority Leader Mitch McConnell (R-Ky.) is under increasing pressure to bring up a revised criminal justice bill despite staunch opposition from conservatives in his own caucus.

The Republican leader has been careful not to take a side on the legislation, even though his second-in-command, Sen. John Cornyn (R-Texas), is one of the bill’s chief supporters.

{mosads}The normally tight-lipped McConnell will need to walk a fine line as he weighs his decision: Is it worth potentially netting another bipartisan victory ahead of the election — when Republicans have to defend 24 Senate seats — if it would put divisions within his own party under a spotlight?

In addition to vocal pushback from a handful of GOP senators — including firebrands such as Tom Cotton (Ark.) and Ted Cruz (Texas) — it could put Senate Republicans on a collision course with Donald Trump.

The GOP’s presumptive presidential nominee, not known for policy specifics, hasn’t weighed in on the Senate’s bill; however, his previous law-and-order leanings are at odds with the legislation.

“I’m tough on crime, and we have to stop crime. You look at what’s going on in the inner cities right now. It’s unbelievable. … Boy, it’s like the Wild West,” he told MSNBC’s “Morning Joe” late last year when asked if he had pivoted away from tough-on-crime policies.

His comments, and the megaphone he’ll have going into November, have sparked a steady stream of media speculation that he could ultimately sink momentum behind sentencing reform on Capitol Hill.

Supporters of the legislation have spent months making revisions to the proposal aimed at winning over more GOP support, but they have one looming hurdle: getting McConnell to agree to bring it up. 

“We need to get to the point where Leader McConnell agrees to bring it to the floor,” Sen. Mike Lee (R-Utah) said during a conference call on the legislation. “It really is ready to go to the floor as soon as we can get Leader McConnell to make that decision.”

They’re expected to step up their efforts to persuade McConnell now that they’ve locked in the changes. Sen. Chuck Grassley (R-Iowa) told reporters before the recess that it’s “time for those discussions” to begin. 

But when McConnell could make his decision is largely uncertain. Don Stewart, a spokesman for McConnell, told The Hill Friday there were no scheduling announcements to make on the bill.

Backers are racing against a limited election-year Senate schedule, where floor time is a scarce resource and is likely to be dominated by McConnell’s time-intensive goal of passing the 12 individual appropriations bills.

Cornyn said the GOP leader would be looking for legislation that has “broad bipartisan support” and “can actually pass,” and that supporters of the legislation have been preparing to sway him using those points.

As the Republican senators try to convince the leader of their caucus, they can also count on the support of outside groups and Democrats, who are clamoring for McConnell to take up the legislation.

Sen. Dick Durbin (D-Ill.) called out the Republican leader, saying he should move the legislation this month and that he believes it currently has 60 votes.

“[Republicans] have really an audience of one: Mitch McConnell,” he said before senators left town for the recess.

A handful of prominent conservatives are also championing the issue, arguing Republicans can’t afford to kick the can until next year.

“Conservatives could be facing four or eight more years of a Democrat in the White House, Democratic control of the Senate, and, quite possibly, the House could swing back to left-wing control,” FreedomWorks CEO Adam Brandon; Timothy Head, the executive director of the Faith and Freedom Coalition; Marc Levin, the policy director for Right on Crime; and Grover Norquist, the president of Americans for Tax Reform, wrote in a National Review op-ed this week.

A coalition of religious groups also sent a letter to McConnell this week urging him to bring up the bill.

“Our communities are on the front lines in neighborhoods ravaged by a broken criminal justice system,” they wrote.

But a move by McConnell to bring up the legislation would set up an inevitable floor fight. GOP opponents of the legislation are showing no signs of willingness to go down quietly.

“The proper thing to do today would be to allow this to play out,” Sen. Jeff Sessions (R-Ala.) — Trump’s sole Senate endorser — told reporters late last month. “See where we are, see where the crime rate is going before we push for another reduction in sentencing.”

The proposal’s skeptics argued the revisions did little to address their concerns that the bill would increase the crime rate and release offenders who could go on to commit additional crimes.

Sen. Orrin Hatch (R-Utah) is also against the legislation, saying it needs stronger protections to defend those who are jailed after unknowingly committing a crime.

Cornyn, however, brushed off suggestions that GOP infighting would ultimately keep McConnell from bringing it to the floor.

“There’s no such thing as unanimous passage of legislation around here,” he told The Hill.

“We have a number of 2016 candidates who have signed on to the legislation,” he added. “That indicates, to me, they think the politics is favorable.”