Big comment from Kavanaugh just now: "I tend to agree with you" that the case is "very straightforward" under our severability precedents. Those precedents (including an opinion authored by Kavanaugh last term) say there is usually a strong presumption in favor of severability.

Kavanaugh could vote to declare the individual mandate unconstitutional (his questions so far suggest he thinks it it) but also vote to sever the mandate and leave the rest of the law in place. He hinted at such an approach last term in this case: https://www.scotusblog.com/case-files/cases/barr-v-american-association-of-political-consultants-inc/

Now arguing: Kyle Hawkins, the solicitor general of Texas. Texas is the lead state among a group of 18 GOP-led states challenging the law.

Roberts now suggests he, like Kavanaugh, is skeptical of the challengers' severability argument. "It's hard for you to argue," Roberts says to Hawkins, that the 2017 Congress intended for the entire ACA to fall if the individual mandate were struck down.

Maybe it's true that some lawmakers would have wanted the court to strike down the full law, but "that's not our job," Roberts says.

Roberts, like Kavanaugh, wrote an opinion last term in which he found one provision of a statute invalid but upheld the remainder of the law.

A very animated Breyer presses Hawkins on his theory that a command to do something, without a penalty, is unconstitutional. Under that theory, Breyer says, all sorts of "hortatory" statements from Congress (such as laws that encourage people to "plant a tree") would be invalid.

Kagan with a trenchant and very Kagan-like question. She notes that the 2017 Congress made the mandate LESS coercive. So "how does it make sense to say that what was not an unconstitutional command before has become an unconstitutional command now?"

Kavanaugh again giving a big signal of his thinking on severability -- this time even more strongly than before. "It does seem fairly clear that the proper remedy would be to sever the mandate provision and leave the rest of the act in place."

So far, Kavanaugh's repeated comments suggesting he is inclined to separate out the individual mandate (rather than striking down the entire ACA if the mandate is deemed unconstitutional) are the most significant development of this morning's oral argument.

Both Kavanaugh and Roberts have suggested this morning that they may view the individual mandate as severable from the rest of the law.

If those two justices join the court's three liberals in finding that the mandate is severable, that would be five votes to save the ACA.

Now arguing: Acting U.S. Solicitor General Jeffrey Wall on behalf of the Trump administration, which has joined the Republican state officials in opposing the ACA. Wall is the final advocate of the day.

Breyer with a low-key vocabulary lesson this morning. Earlier, he was asking about "hortatory" statutory provisions. Now he wants to know about "precatory" language. Breyer has lots of fancy synonyms for the concept of encouragement.

Sotomayor asks Wall an interesting hypo: If Congress had temporarily phased out the mandate penalty, and then scheduled to phase it back in in future years, would that be constitutional? Wall says yes.

Sotomayor says that shows that a zero-ed out tax can still be a tax.