One of the most controversial parts of the U.S. Supreme Court ruling on the Affordable Care Act allows states to opt out of expanding Medicaid coverage in 2014.

The expansion is one of the first and most important decisions North Carolina’s next governor will make, but the question is receiving little attention on the campaign trail as the candidates appear unsure of what to do.

In North Carolina, where roughly one in five residents is uninsured, the expansion would initially add roughly 525,000 residents to the program. The number grows to 560,000 by 2019 with about 75 percent of those currently not insured.

Republican candidate Pat McCrory’s campaign indicated he opposed taking millions in federal money to cover the new recipients, expressing concern about the cost. “It would be irresponsible for North Carolina to now automatically accept the federal money before knowing the immediate and long-term costs of the law and its impact on our already fragile economy and budget,” the campaign said in a statement.

But later, McCrory appeared to soften his stance, telling reporters last week: “I think one of the options might be to turn it down. But I don’t think there is enough information about what those ramifications are. We don’t know the rules and procedures.”

His Democratic rival, Walter Dalton, hasn’t made a decision. “It’s a big issue involving a lot of money and a complex decision. He needs to study it further,” campaign spokesman Schorr Johnson said.

In other states, Republican governors like Rick Perry in Texas and Nikki Haley in South Carolina already have made it clear that they don’t want the federal money for ideological and financial reasons.

For the first few years, the federal government would pay the entire cost for newly eligible people. The reimbursement will drop to 90 percent by 2019. Typically, Medicaid pays two-thirds of the state’s costs, and the state pays the rest. Under the health care law, the expansion would cover anyone earning less than 138 percent of the federal poverty level, or roughly $32,000 for a family of four.

The state Medicaid office estimated that adding 560,000 people to Medicaid would cost the state $830 million over six years and bring in $15 billion in federal money. The bulk of that cost is not from the newly eligible people – but rather those currently eligible who are not on the Medicaid rolls.

“We are going to pay whether we expand or not,” said Pam Silberman, the president of the N.C. Institute of Medicine.

The N.C. General Assembly is studying the issue and waiting for the new governor’s input, said Rep. Nelson Dollar, a Cary Republican and Medicaid expert. “From the initial numbers, it looks very problematic as to where the money would come from to afford the expansion,” he said.

Gov. Bev Perdue’s office said last week that it is still reviewing aspects of the Medicaid issue.

Staff writer Rob Christensen contributed to this report.

Frank: 919-829-4698