Final answer:
Exchange enrollees, particularly those with lower incomes, are the most affected by rising health insurance premiums.
Step-by-step explanation:
Rising health insurance premiums primarily affect exchange enrollees, especially those with incomes less than 250 percent of the federal poverty level. Insurance companies often charge higher prices to individuals with pre-existing medical conditions or deny them coverage altogether. Prior to the Affordable Care Act, more than 32 million Americans were uninsured, leading to rising healthcare costs.