ASHEVILLE, N.C. — Jane and Abe Goren retired here five years ago to escape the higher cost of living they had abided for decades in the suburbs of New York City. They did not anticipate having to write monthly checks for health insurance that would exceed their mortgage and property taxes combined.

Ms. Goren, 62, is paying nearly $1,200 a month for coverage through the individual insurance market (her husband, 69, is on Medicare) and accumulating enough debt that her sons recently held a fund-raiser to help. For next year, her insurer, Blue Cross and Blue Shield of North Carolina, has proposed raising premiums by an average of 22.9 percent, a spike it is blaming squarely on President Trump.

For months, the Trump administration has threatened to stop billions of dollars in payments that lower out-of-pocket medical costs for nearly six million low-income patients. Mr. Trump’s hedging has created deep uncertainty in the Affordable Care Act markets, the impact of which may become clearer on Wednesday, the deadline for insurers to say whether they plan to sell next year on the federal marketplace created under the health law and to file rate requests.

North Carolina has more than 300,000 people benefiting from these “cost-sharing” subsidies, which reimburse insurers for absorbing the deductibles and co-payments of low-income customers. The Affordable Care Act requires that these customers’ out-of-pocket costs be lowered one way or another. If the federal government stops reimbursing insurers, many insurers have said they will make up for it by raising premiums.