Covid’s rampage through the country’s nursing homes killed more than 172,000 residents and spurred the biggest industry reform in decades: a mandate that homes employ a minimum number of nurses.

But with President-elect Donald Trump’s return to the White House, the industry is ramping up pressure to kill that requirement before it takes effect, leaving thousands of residents in homes too short-staffed to provide proper care.

The nursing home industry has been marshaling opposition for months among congressional Republicans — and even some Democrats — to overrule the Biden administration’s mandate. Two industry groups, the American Health Care Association and LeadingAge, have sued to overturn the regulation, and 20 Republican state attorneys general have filed their own challenge.

Consumer advocates, industry officials and independent researchers agree that the incoming administration is likely to rescind the rule, given the first Trump administration’s “patients over paperwork” campaign to remove “unnecessary, obsolete, or excessively burdensome health regulations on hospitals and other healthcare providers.” Among other things, Mr. Trump aided the industry by easing fines against homes that had been cited for poor care.

“The Trump administration has proven itself really eager to reverse overreaching regulations,” said Linda Couch, the senior vice president for policy and advocacy at LeadingAge, which represents nonprofit elder care providers. “We think it’s got a pretty good chance of being repealed, and hope so.”

Issued in April, the staffing regulation requires nursing homes to have registered nurses on site around the clock — something that the industry has endorsed — and to maintain minimum numbers of nurses and aides. Four of five homes would have to increase staffing. The requirements would be phased in, starting in May 2026.