WASHINGTON (AP) — The Supreme Court is hearing arguments in a major test of President Barack Obama's health overhaul that threatens insurance coverage for millions of people.

The justices are meeting Wednesday to try to determine whether the law makes people in all 50 states eligible for federal tax subsidies to reduce their insurance premiums. Or does it limit tax credits to people who live in states with their own health insurance marketplaces?

A ruling limiting where subsidies are available would have dramatic consequences because roughly three dozen states opted against their own marketplace, or exchange, and instead rely on the federal healthcare.gov. Independent estimates say 8 million people could lose insurance coverage.

Opponents of the Affordable Care Act failed to kill the law in an epic Supreme Court case in 2012.

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