The expansion of Medicaid allowed under the Affordable Care Act has outperformed its parent program, especially in New Jersey. While national enrollment in ACA plans has fallen 15 percent just since spring, Medicaid has reduced the share of New Jerseyans without health coverage while saving the state significant money - for now.

Gov. Chris Christie, who was the eighth Republican governor to opt for Medicaid expansion despite opposition to Obamacare, announced at the end of last month that 566,655 additional residents have joined NJ FamilyCare, the state's version of Medicaid. With the higher earnings limits for Medicaid eligibility, NJ FamilyCare now serves 1.7 million low-income and disabled residents.

As of last year, just 8.7 percent of people in the state - 770,000 - didn't have health insurance, down from 1.1 million in 2011, the Census Bureau's American Community Survey showed last week.

The gains have been significant in South Jersey. Those with health insurance increased in the period to 91.5 percent in Atlantic County (from 85.5 percent), to 89.5 percent in Cumberland County (from 84.5), to 90.9 percent in Cape May County (from 88.3), and from 91.5 percent to 93.3 percent in Ocean County, according to an analysis by NJ Spotlight.

Expanded Medicaid also has saved money. The state estimates it will have net savings of $353 million this fiscal year and $355 million the next, reflecting lower payments to hospitals for charity care, increased revenue from state tax on health plans and savings on group coverage.

Christie said the state expenditure per Medicaid beneficiary decreased from $9,690 in fiscal 2014 to $8,940 in fiscal 2015.

This comes after a study early in the year found the share of New Jersey children without coverage had dropped from 6.3 percent to 4.8 percent, with the biggest gains among Hispanic children and South Jersey cities benefiting substantially.

Still, the broader health coverage at what seems a lower cost could turn out to be temporary.

So far, the Affordable Care Act has paid the entire cost of additional people covered under Medicaid. Starting next year, New Jersey will pick up 5 percent of the cost and the following year 10 percent. As the ACA struggles to keep its coverage exchanges functioning despite the withdrawal of major insurers, the federal government may choose to shift more of the Medicaid cost to New Jersey and other states.

Knowing this, Christie said he's "not for Medicaid expansion at any price" and acknowledged it will be future governors who must evaluate the federal program's continued cost-effectiveness.

As we've said before, the coverage gains are certainly worthwhile and in a well-configured insurance and care system should be affordable to society. But clearly more health care reform is needed to make them sustainable.

Our view