That, too, was an outrageous position. It flouted the Justice Department’s duty to defend, a solemn duty, and one that goes to the heart of the rule of law. Without it, the sitting administration could pick which laws it wanted to defend in the courts and which it wanted to abandon. Laws could rise or fall based on nothing more than partisan disagreement. That’s inconsistent with a constitutional system that assigns to Congress — not the president — the power to legislate.

And so, at the confirmation hearing on his nomination to become attorney general, Mr. Barr said that he would review the Justice Department’s position in the Texas lawsuit. Apparently he did just that — but instead of mounting a vigorous defense, he doubled down on killing Obamacare. It’s as if Mr. Barr said to his predecessor, Jeff Sessions: “You thought your position was crazy? Hold my beer.”

Does the administration really think that the very position it advanced just months ago is so untenable that it must now adopt one that is even more extreme?

The shift in legal position won’t make much of a difference in the lawsuit itself. Because a group of blue states has intervened, the appeals court will hear a full-throated defense of the law. Most observers expect the court to uphold the Affordable Care Act; if so, the Supreme Court may choose not to hear the case.

But the Trump administration has signaled loud and clear that its campaign against Obamacare is not over; that it will stop at nothing to achieve in court what it could not achieve in Congress; and that it doesn’t care how many people are hurt if the Affordable Care Act is undone.

It has also put health care back at the center of the political conversation. Republicans already took a beating on the issue in the fall midterm elections, and Democrats, who released a bill in the House to strengthen the Affordable Care Act, want to keep running on it. They’ll be sure to remind voters of the Trump administration’s zealous commitment to taking away their health care.

Along the way, the Justice Department has trashed the duty to defend. That’s not to be taken lightly. The duty is a close cousin to the president’s constitutional duty to enforce the law. If the Justice Department really thinks that Obamacare is so blatantly unconstitutional that it can’t be defended, that implies that the president is violating the Constitution whenever he applies it.