Aetna’s decision to pull back from ObamaCare is fueling new questions about the long-term viability of the Affordable Care Act (ACA).

When UnitedHealthcare announced in April that it was leaving most ObamaCare marketplaces in 2017, supporters of the law argued against drawing broad conclusions, calling it one company’s decision.

But since then two other large insurers, Humana and Aetna, have said they are slashing ObamaCare offerings due to heavy financial losses from the plans.

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