Graduate students have long relied on health insurance subsidies awarded as part of financial-aid packages as they try to earn a living and a degree.

But the future of that benefit could be jeopardized by the Internal Revenue Service’s interpretation of a provision of the Affordable Care Act that casts the subsidies as an attempt to elude ACA’s employer mandate.

Seventeen U.S. senators, including Virginia Sens. Mark R. Warner and Timothy M. Kaine, both Democrats, wrote a letter last month urging the Obama administration to clarify the IRS language and warning that it runs counter to ACA’s primary goal to expand insurance coverage.

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