The decision is big for state governments under President Obama's 2010 overhaul of health insurance laws. Originally, states were to have been required to expand Medicaid, the joint state-federal insurance program for low-income people, or face penalties.
But last year, the U.S. Supreme Court threw out the penalties, leaving it up to states to decide whether to participate. The federal expansion is effective Jan. 1, 2014.
"I'm starting to feel more optimistic" about winning Christie's support, said Dena Mottola Jaborska, program director at New Jersey Citizen Action, one of several groups participating in the NJ for Health Care Coalition, which is campaigning for the expansion. "The governor does care about working people who work hard and play by the rules."
New Jersey is relatively generous when it comes to insuring children and their low-income parents.
But only a small number of non-senior, non-disabled adults with no children qualify for the government-run insurance known as NJ FamilyCare. A single person has to make less than $2,800 a year to qualify for Medicaid now. As of last month, 1.3 million people in New Jersey were on Medicaid and FamilyCare, including 44,000 non-disabled, low-income adults on Medicaid.
Under the federal Medicaid expansion, eligibility would be extended to people in that situation who make up to $15,415. In an analysis of census data, the think tank New Jersey Policy Perspective, part of the NJ for Health Care group, found that about 176,000 New Jersey residents - about one-fourth of the state's 700,000 uninsured adults - would be eligible for an expanded Medicaid program.
New Jersey Policy Perspective says in its report most who would be newly eligible work in low-wage jobs in such fields as food service and landscaping.
Danielle Sacripante, 55, a graphic designer in Ewing, has not had a full-time job in more than three years. She cobbles together part-time jobs in her field, in retail, and even by modeling nude for art students, and has been making $15,000 to $20,000 a year.
In her leanest years, she would have qualified for an expanded Medicaid program. But as it is, she has been without insurance except for a short period when she was working part time for $8.75 an hour and paying about $100 a month for a limited plan.
Sacripante is using a charity-care program to pay for hip surgery next month but would like to have some insurance plan. She would prefer that it come through a job, but she says finding full-time employment is difficult.
"There are so many people out there that need health insurance," she said.
Under the Affordable Care Act, the federal government would pay all costs of the expansion from its launch in 2014 through 2016 and at least 90 percent after that. For three years, the federal government would pay the full cost of covering people already on Medicaid, a cost now shared with the state.
Raymond Castro, a former state human services official who wrote the New Jersey Policy Perspective report, said he believed there would be immediate and lasting savings for the state, not only because of the larger federal contribution, but also because the state could cut payments to hospitals that provide charity care. Also, a provision of the federal law would let eligible people sign up for Medicaid at any time, including at a hospital.
With more people covered, he said, there would be less need for charity-care funds. And that's what makes hospitals a bit apprehensive.
"By and large, in principle, we do support the concept of expanding Medicaid," said Randy Minniear, a senior vice president at the New Jersey Hospital Association.
But he said the group wanted to make sure the finances work - it has commissioned a study - before advocating for it more aggressively.
Doctors have reservations, too.
Mary Campagnolo, president of the Medical Society of New Jersey, said she was concerned that expanding Medicaid would not help with the state's shortage of primary-care doctors, especially those who take Medicaid patients.
"If we were to expand Medicaid without enough access, it's going to be very difficult," she said.
Even a provision of the Affordable Care Act that would more than double Medicaid payments to primary-care doctors might not relieve that problem, she said. The bigger payments would be guaranteed for only two years.
There's another, blunter criticism of the expansion: The state eventually would have to pay some costs of expanded coverage. A study last year found the expansion would cost New Jersey nearly $1.5 billion through 2022. Without the promised offsetting saving, taxpayers would have to pick up that bill.
Steve Lonegan, director of the New Jersey branch of Americans for Prosperity, one of few groups actively campaigning against expanding the program, says the state, with its history of debt, would not have the discipline to save any money.
"At some time, people have to suck it up and fend for themselves, just like my grandparents did when they came here from Italy," said Lonegan, a former mayor of Bogota and a two-time candidate for governor.