One of the thorniest issues facing the bipartisan stimulus negotiations is the insistence by Senate Republicans that businesses and other entities have sweeping immunity from coronavirus-related lawsuits.

Many Democrats have refused to agree to such language, saying it could imperil workers.

But now both sides are attempting to craft a compromise on the “liability shield,” worried that the prolonged impasse could derail the broader spending bill at a time when the economy appears to be softening.

Treasury Secretary Steven Mnuchin, in a statement on Tuesday night, said that the White House’s latest offer of a $916 billion package included “robust liability protections for businesses, schools, and universities,” illustrating how the issue remains paramount for Republicans.

A half-dozen senators met on Monday night in the Mansfield Room in the Capitol, and multiple lawmakers expressed renewed optimism about the possibility of a deal being within reach, but the liability issue will have to be resolved.

Sen. Mitt Romney (R-Utah), one of the architects of the $908 billion bipartisan stimulus plan that revived talks last week, on Monday proposed that immunity from federal lawsuits should only last through this year, according to a draft of his plan circulating among the bipartisan group. The measure would provide an exemption, allowing suits over gross negligence or willful misconduct. Senate Majority Leader Mitch McConnell (R-Ky.) and other senior Republican lawmakers have proposed that the liability shield cover five years.

Sen. John Cornyn of Texas, the lead author of the GOP’s liability shield plan, left the bipartisan discussions early on Monday night. But he and Sen. Lindsey O. Graham (R-S.C.), a close ally of the president, have been involved in crafting a liability compromise, and they are expected to work on a proposal with opposing senators, including Richard J. Durbin (D-Ill.) and Angus King (I-Maine).

At issue is how much liability companies should face if workers or customers seek redress for personal harm caused by infections. Aides also cautioned that how to apportion state and local funding has also proved a difficult sticking point in economic relief negotiations, which also threatens to derail talks. And the talks remained in flux on Tuesday, with the White House pushing Senate Republicans to consider adding $600 stimulus checks to the package as well.

With just weeks remaining for lawmakers to reach an agreement before federal emergency relief programs expire, the impasse over legal liability could sink much wider efforts to provide hundreds of billions of dollars in aid to jobless Americans, struggling municipalities and hard-hit small businesses.

Romney told reporters Tuesday morning that the negotiations were advancing, saying that King had offered a compromise on the issue that would help head off excessive litigation.

“There was a real advance last night that came from Lindsey Graham and Angus King, and hopefully they’ll keep pushing ahead,” he said.

Senate Democrats have not backed Romney’s plan but cited progress in negotiations on Monday. “Tonight was a very good night,” said Sen. Joe Manchin III (W.Va.) after leaving the meeting devoted to the liability issue. He also noted “very bright individuals who feel very good about it, and we’re just moving along.”

Republicans and business groups have been pushing the liability shield since this spring. McConnell called the liability shield a red line in negotiations in May, saying that a flood of lawsuits could amount to a “second pandemic” and deeming the measure necessary to protect companies.

“This is not just about businesses. It’s about universities, charities and others who see this developing epidemic of lawsuits headed their way,” McConnell told reporters on Tuesday, adding that the immunity was not “total” in the GOP proposal.

It is unclear whether McConnell will ultimately support whatever compromise language the bipartisan group may develop. McConnell on Tuesday floated a deal that left out both the liability shield and state and local aid, the two most controversial provisions. But at a news conference shortly afterward, Senate Minority Leader Charles E. Schumer (D-N.Y.) appeared to attack that idea, angrily accusing McConnell of putting the livelihoods of firefighters, sanitation workers and police officers in jeopardy.

Democrats have characterized the liability shield as a nonstarter, alleging that the Trump administration’s lax stance on worker protections has already tilted the scale toward companies on safety issues. Durbin, who had been involved in the bipartisan group’s work, pulled out of discussions last week and criticized the inclusion of a liability shield in the legislation.

Lawmakers have more information now than they did in the spring about the potential for virus-related lawsuits. And data shows that the potential “flood” of litigation raised by Republicans and business groups has not come.

An online complaint tracker from the law firm Hunton Andrews Kurth shows that out of an overall pool of about 6,500 lawsuits filed across the country so far, only 116 have been filed by employees over issues such as lack of personal protective equipment, exposure or infections at work, and death. Consumers have filed an additional 29 personal-injury or wrongful-death claims related to virus exposure.

“That’s like two to four lawsuits per state,” said Hugh Baran, an expert on legal recourse for employees at the worker-focused National Employment Law Project. “That’s a trickle. It’s not a flood. … This whole immunity bill that’s been proposed by McConnell and Cornyn is really a solution in search of a problem.”

The legal database Lex Machina counts 234 personal-injury and wrongful-death cases filed against companies for virus-related issues as of the end of November, mostly negligence suits from clientele of cruise lines and assisted-living facilities. An additional 527 lawsuits have been filed by employees over virus issues, mostly workers claiming they were retaliated against or terminated for getting sick. Both of those figures represent a small fraction of the total court cases in those practice areas filed this year, including non-virus cases: 16,461 personal-injury and wrongful-death suits and 17,822 employment cases.

“Cases caused by covid-19 have not hit the federal courts in a particularly large wave at this time,” said Rachel Bailey, a legal analyst at Lex Machina.

By contrast, the businesses themselves appear to be a much larger source of litigation than employees: About 1,300 lawsuits have been filed by companies against insurers over business interruption claims because of the coronavirus, for example. Lawsuits that track with conservative-leaning complaints, including nearly 1,000 lawsuits counted by Ballotpedia against local and state coronavirus restrictions, have also accounted for a significantly larger bulk of the legal cases during the pandemic.

Legal advocates and worker representatives say that allowing workers to challenge employers through private lawsuits is a crucial check on corporate power at a time when the federal Occupational Safety and Health Administration has taken a largely pro-employer approach to safety issues.

The agency was slow to issue citations early in the pandemic, declined to set enforceable workplace safety standards for the coronavirus, and watered down its guidelines for companies with terms such as “if feasible” and “when possible.” In some particularly high-profile cases, the fines that it has issued have been paltry.

Democrats are also hoping to extend the paid leave provisions from the first stimulus, which granted workers at companies with less than 500 employees paid leave for sick time, or to care for sick family members and children left without childcare.

A new estimate from the House’s Joint Committee on Taxation estimated that extending those paid leave provisions would cost $1.35 billion for 2 months — more than 85 percent less than previous two-month estimates, an indication that paid leave has proved cheaper than initially thought.

A liability shield bill proposed by Cornyn in summer offers a window into what Republicans want: The bill prohibited lawsuits against businesses, nonprofit entities and local government branches that are following public health guidelines, except in cases of gross negligence or willful misconduct. The bill also appears to exempt companies from some OSHA enforcement activity — a significant issue given the likelihood that the Biden administration will steer the agency to more aggressively prioritize worker safety in the new year.

“Timely, targeted and temporary liability protections against unfair COVID lawsuits is absolutely critical for employers working hard to follow public health guidelines,” Harold Kim, president of the Chamber of Commerce’s Institute for Legal Reform, said in a statement.

Democrats have overwhelmingly criticized the liability shield, with Sen. Bernie Sanders (I-Vt.) going as far as saying he would vote against the overall package if the liability shield is included. Other Democrats have said they oppose the idea but are willing to try to find common ground with Republicans on it to secure passage of the broader legislation.

“This is the reality: In order to gain Republican support — and remember we have to have 60 votes — some liability protection will be part of the package,” said King, who caucuses with the Democrats and was one of the early backers of the bipartisan liability proposal.

The U.S. government has not done a detailed study of the proportion of coronavirus infections that have spread through workplace contact, but workplace transmissions are thought to have generated a significant portion of the pandemic’s caseload so far. About 300,000 nursing home staff members alone have fallen ill, for example, and 254,000 health-care workers; more than 1,600 of those workers have died.

A Harvard study of data from six Asian countries early on in the pandemic found that possible work-related transmission accounted for 47 percent of initial outbreaks. In Oregon, where the state health authority is tracking workplace outbreaks with five or more cases, there have been at least 11,139 cases from workplaces, about 15 percent of the state’s total. Approximately 7 to 9 percent of deaths in the United States are from workers bringing infections home to their families, according to one estimate.

There are already significant barriers in place to prevent a flood of lawsuits from workers who get sick or injured on the job.

The legal particulars differ state to state, but typically worker injuries and deaths are dealt with through the workers’ compensation system, where the burden of proof is much lower than in a courtroom and damages are capped. The threshold for such lawsuits is high — typically an employee or their family would have to show it was the result of gross negligence or an intentional act on the part of an employer.

“It’s going to be some extraordinary level of fault on behalf of the employer, and that’s going to be tough to prove,” said David L. Barron, an employment lawyer at Cozen O’Connor.

Barron said that employment lawyers had been batting around a few theories about why the wave of cases hadn’t materialized, including that it could still be forthcoming in the future.

According to lawmakers and aides familiar with the negotiations over the bill, the debate has included discussion of whether companies should face different liability standards for their actions early in the pandemic, when government public health guidance was inconsistent and rapidly changing, compared to later on.

Lawsuits have served an important purpose: Even those that have already been dismissed, worker advocates say, provided a window into some of the more egregious allegations of misconduct by some companies.

“People have rights that need to be addressed in the court system,” said Michael E. Levine, who represents the family of deceased grocery worker Gerardo Gutierrez, who is suing his employer, the Florida grocery chain Publix. “Businesses should be held accountable when they’re not keeping their workforce safe, and when they’re taking away the rights of their employees to keep themselves healthy.”

Gutierrez, who was 70, had asked his employer whether he could wear a face covering at his South Beach store in Miami, but he was denied, according to the complaint.

A lawsuit filed against poultry producer Tyson Foods, where at least six workers died after an outbreak at a facility in Iowa this year, said that a manager had organized a betting pool for supervisors to wager how many workers would get sick. Tyson has declined to comment on the allegation.

Amazon changed its policy about hand-washing at a facility in New York after workers there filed a lawsuit alleging a lack of adequate safety protections. (Amazon CEO Jeff Bezos owns The Washington Post.)

“If workers are safe, consumers can have confidence in going out. That’s what we need to rebuild the economy,” Levine said.