Over at The Commonwealth Fund, health-law prof and ACA expert extraordinaire Tim Jost properly focuses not on whether CJ Roberts got it right when he upheld the individual mandate as a proper exercise of Congress's powers under the Taxing Clause of the Constitution (Judge Barrett has argued that he did not) or when he upheld access to ACA premium tax credits for individuals enrolled in insurance plans through the federal exchange (ditto).
The issues presently before the Court in California v. Texas are (1) whether the individual mandate is unconstitutional now that Congress has zeroed out the tax penalty in the 2018 tax reform bill and, if so, (2) whether the individual mandate provision is severable from the rest of the ACA. The district court (N.D. Tx., Fort Worth Div.) and the Fifth Circuit both answered (1) yes and (2) no, meaning the whole ACA has to be thrown out. Texas v. California, which has been consolidated with California v. Texas, raises a third issue: Whether the individual and state plaintiffs in this case have established Article III standing to challenge the ACA's individual mandate. In the unlikely event that Judge Barrett isn't confirmed before the Court decides these cases, the standing issue could conceivably give a Court split 4-4 on the first two questions a way out. Lack of Article III standing requires dismissal of the case at the district court level, effectively nullifying the two lower-court decisions.
As Tim Jost writes,
Though she could be asked about standing or the mandate’s constitutionality, questions for Judge Barrett should mainly focus on severability: How much, if any, of the ACA should be invalidated if the mandate is found unconstitutional? (It does not matter much if the unenforceable mandate is invalidated if the rest of the ACA remains in place.) Would she disturb the Court’s long-standing presumption of severability? Cases recently decided by the Court with majority opinions written by Chief Justice Roberts and Justice Kavanaugh reinforce the presumption that if a provision of a statute is found unconstitutional, as much of the rest of the statute as possible should be found severable and preserved. She should be asked if she agrees with this doctrine.
Severability goes to the heart of these two cases. It is nearly inconceivable that she would tip her hand on this issue during the hearings. Democrats will fume and threaten not to vote to confirm, but most of them weren't going to vote for her confirmation anyway, and Mitch McC has enough Republican votes lined up to confirm the judge without the Dems.