Viorel Florescu/Staff photographer

Ariel Cordero helping Ana Morales and her son, Oscar, 6, sign up for health insurance in Passaic in January. The U.S. Supreme Court will hear a challenge to the Affordable Care Act on Wednesday.

The U.S. Supreme Court will hear arguments Wednesday on a challenge to the Affordable Care Act that would end the federal subsidies for people who bought health coverage on the federal marketplace, a decision with enormous potential impact in New Jersey and not just for the 210,000 insured residents directly affected.

The loss of subsidies which average $309 a month for eligible consumers in New Jersey would make it difficult for many recipients to afford to continue insurance coverage, experts say.

The ripple effects could be substantial. Without the subsidies, the ranks of uninsured in New Jersey would grow, leading tens of thousands of people to fall back on charity care and putting more stress on hospitals and other health care providers, according to the state hospital association and groups that have filed briefs with the court.

States that want to protect consumers who have used the financial help to buy insurance will scramble to find ways to maintain the funding. For Governor Christie, who opposes Obamacare and vetoed legislation to establish a state-run marketplace as too costly, an adverse Supreme Court decision would present a difficult situation.

In addition, if residents pull out of the Obamacare plans in large numbers, it would push premiums up for those who continue in them, insurers say. The subsidy shutdown, as some call it, would be especially damaging to the newest insurance companies, for whom the majority of customers come from the federal marketplace, according to briefs filed with the court. If those companies exit the state or fail, competition and choice will be reduced not to mention care disrupted for their members.

A ruling against the Obama administration would be very consequential far beyond the people who would lose their subsidies, said Joel C. Cantor, director of the Rutgers Center for State Health Policy. It would have dramatic consequences for hospital finances and competition in the marketplace.

If the court ended subsidies and chose not to allow a transition period for officials to remedy the situation, there will be chaos in health insurance markets, millions will become uninsured and premiums will spike for millions more across the country, he said. This could happen as early as this summer.

Republicans have long fought the health overhaul as an overreach of government authority that they say drives up health costs, kills jobs and wastes taxpayer money. The most recent of dozens of votes in the House of Representatives to repeal it took place Feb. 3. The challenge to be heard by the justices this week initially was dismissed by the administration and its allies as an insubstantial threat.

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Supreme Court decision on health care subsidies could affect thousands in N.J.