Devon Campbell-Williams, an inmate serving time for assault in the Multnomah County Inverness Jail in Portland, Ore., applied for Medicaid in January with the help of an eligibility worker hired by the county to enroll inmates. When he gets out of jail in May, he said, he will have health insurance for the first time, coverage that will allow him to get treatment for his ankle, which he broke in 2007 and has been bothered by ever since.

“It’s going to mean a lot,” Mr. Campbell-Williams said, adding that in the past, “I just went to the hospital, that was really about it.”

Opponents of the Affordable Care Act say that expanding Medicaid has further burdened an already overburdened program, and that allowing enrollment of inmates only worsens the problem. They also contend that while shifting inmate health care costs to the federal government may help states’ budgets, it will deepen the federal deficit. And they assert that allowing newly released inmates to receive Medicaid could present new public relations problems for the Affordable Care Act.

“There can be little doubt that it would be controversial if it was widely understood that a substantial proportion of the Medicaid expansion that taxpayers are funding would be directed toward convicted criminals,” said Avik Roy, a senior fellow at the Manhattan Institute, a conservative policy group.

Language in the health care law also allows private insurance plans purchased through state exchanges to cover health care for people who are in jail awaiting trial, even in states that have not expanded Medicaid. But few prisoners have incomes high enough to afford the plans, even with federal subsidies, and most state and county correction systems are not yet set up to benefit from that coverage.

In the past, states and counties have paid for almost all the health care services provided to jail and prison inmates, who are guaranteed such care under the Eighth Amendment. According to a report by the Pew Charitable Trusts, 44 states spent $6.5 billion on prison health care in 2008. In Ohio, health care for prisoners cost $225 million in 2010 and accounted for 20 percent of the state’s corrections budget. Extended hospital stays — treatment for cancer or heart attacks or lengthy psychiatric hospitalizations, for example — are particularly expensive.

Stuart Hudson, managing director of health care for Ohio’s Department of Rehabilitation and Correction, said his department, which plans to start enrolling inmates in Medicaid when they have been in the hospital for 24 hours, expects to save $18 million a year through the practice, “although it’s hard to know for sure, because there’s other eligibility factors we have to keep in mind.”