A federal appeals court seemed likely on Tuesday to strike down what remains of the Affordable Care Act's individual mandate, but sent more mixed signals about its willingness to throw out the rest of the health care law along with it.

Why it matters: If a ruling striking down ACA comes to pass — like the one a lower court handed down last year — it would throw some 20 million people off their coverage, create ripple effects through almost every facet of the health care system and ignite an enormous political firestorm.

The case that the mandate itself is constitutional didn’t get much traction Tuesday before a panel of the 5th Circuit Court of Appeals. But the panel’s two Republican appointees wrestled with how to approach the rest of the law — whether to throw it all out, or to send the question back to a lower court.

How it works: The Affordable Care Act requires most Americans to have health insurance and pay a tax penalty if they don't.