Question

What expressed power did the Supreme Court cite when it upheld the constitutionality of the Affordable Care Act?

Answer 1

The expressed power the Supreme Court cited when it upheld the constitutionality of the Affordable Care Act (ACA) was: the power to tax.  

Explanation

Even though the Supreme Court declared that the law could never be upheld, by a decision based on the regulatory power of Congress, the Court ended accepting that it was constitutional and valid for the Congressional power to tax, as a consequence, defending the individual mandate.