President Donald Trump and GOP lawmakers, seeking to regroup following the collapse of the effort to repeal the Affordable Care Act, have an option for gutting the health law relatively quickly: They could halt billions in payments insurers get under the law.

House Republicans were already challenging those payments in court as invalid. Their lawsuit to stop the payments, which they call illegal, was suspended as Republicans pushed to replace the ACA, but it could now resume—or the Trump administration could decline to contest it and simply drop the payments. Mr. Trump could unilaterally end the payments regardless of the lawsuit.

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