Nearly 55,000 fewer Pennsylvanians were getting medical assistance in December 2012 compared with July, according to a new state Department of Public Welfare report, in many cases as an apparent side effect of the elimination of another program.

The numbers represent the third major drop in public insurance rolls since Gov. Corbett took office three years ago.

The precise reasons for the latest decline are unclear. Several changes in the state-funded program took effect simultaneously in August, although a Welfare Department spokeswoman said Friday that none of them pushed people off insurance. She said those affected decided not to reapply.

Some advocates for the poor saw the decline as intentional.

The drop was in the General Assistance program, which in recent years provided medical coverage for about 130,000 low-income adults in two categories statewide.

One is when astronomical medical expenses take most of people's money. The other is for those with physical or mental disabilities so severe they cannot work, and for those caring for someone with an illness or disability, those in drug or alcohol treatment, and victims of domestic violence. This larger group was also eligible for cash assistance - up to $205 a month in Philadelphia - until August, when the General Assembly eliminated the cash but continued the medical coverage.

Most of the drop in medical-assistance rolls since then was in that group.

"They just didn't come in and reapply for the program," said Anne Bale, a DPW spokeswoman. "Once the cash program was gone, there was some apathy in participating in the renewal process" for medical coverage, she said.

She said she did not know why.

Everyone agrees that at least some people didn't need the insurance. A few months ago, however, large numbers of people began "coming in saying they have suddenly lost their medical benefit," said senior attorney Richard P. Weishaupt of Community Legal Services of Philadelphia, "and they don't know why."

He said some may not have reapplied because the loss of cash assistance left them homeless and unable to receive letters from the state in time.

Weishaupt has blamed past drops in coverage on ignorance in Harrisburg and mismanagement in the county welfare offices, which he said were so overloaded that paperwork gets lost and phone calls go ignored. Though that is still true, he said, it also is starting "to look like some sort of concerted attack on this group."

Beth Balaban, who examined the numbers as senior budget analyst for the state House Democratic Appropriations Committee, said she suspected two sets of rule changes enacted last year played a major role.

One made it more difficult to qualify for the temporary disability that allows medical assistance, she said. The other expanded a mandate that adults with huge medical expenses work at least 100 hours a month. Parents with custody of their children had been exempted; now they must work.

"How do you work 100 hours a month if you have cancer, if you have whatever the condition was that got these folks into the program?" Balaban asked.

Bale, the DPW spokeswoman, said rule changes had not been suggested as a reason for the decline when she discussed the numbers with agency officials.

She also disputed any suggestion that there was a continuing pattern to the enrollment decreases.

Shortly after taking office in 2010, Corbett declined to continue adultBasic, a state insurance program for 41,000 low-income working people that was started with tobacco-settlement money during Republican administrations a decade ago and expanded by Gov. Ed Rendell, who negotiated voluntary payments from the Blue Cross insurers.

Then, in 2011, children's enrollment in Medicaid dropped by 90,000 after the DPW ordered expedited reviews of a backlog.

The latest decline may become part of the legislative debate about whether to expand Medicaid under President Obama's health-care overhaul. Corbett opposes expansion under the current rules.

If the state accepts the expansion, said Jonathan Stein, general counsel for Community Legal Services, "every one of these 55,000 people" would be 100 percent covered by Washington, gradually dropping to 90 percent. Currently, the state foots the bill.

Contact Don Sapatkin at 215-854-2617 or dsapatkin@phillynews.com.