Oregon aggressively expanded its Medicaid rolls under the Affordable Care Act, adding enough people to leave only 5 percent of its population uninsured — one of America’s lowest rates.

Now, with the reduction of a federal match that covered those enrollees, the state is calling on voters to decide how to pay for its ballooning Medicaid costs.

A special election on Tuesday asks Oregonians whether they approve of a tax on hospitals, health insurers and managed care companies that would leave Medicaid, as it is now, untouched. More than 1 in 4 residents here rely on it.

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