The administration declined to say anything more specific about what it would do if it gets its way. Caitlin Oakley, a spokeswoman for HHS, declined to answer detailed questions about its plan if the lawsuit succeeds. She referred the questions to the Justice Department.

“The Department of Justice has determined that the district court’s comprehensive opinion came to the correct conclusion and will support it on appeal,” DOJ spokeswoman Kerri Kupac said in an email.

Seema Verma, the administrator of the Centers for Medicare and Medicaid Services, has previously said that the administration wants to preserve coverage for people with pre-existing conditions and has contingency plans if the law is overturned. A spokesman for her agency didn’t respond to detailed questions about what those plans were.

Some Senate Republicans said that while Trump didn’t offer any details on what health care in the U.S. might look like if the states’ challenge succeeds, they said it was too early to be certain.

“I don’t think you can really rethink health care until you know if Obamacare will be part of the system,” said Senator Roy Blunt of Kansas.

Democrats Pounce
Democrats seized on the change in the administration’s position, arguing that it reversed promises that President Donald Trump and Republican lawmakers had made in the midterm election campaign.

“This is an escalation of the Trump administration and Republicans’ attacks on protections for people with pre-existing conditions,” said Senator Chuck Schumer, the New York Democrat and minority leader, in a speech Tuesday. “From the moment this administration and this Republican majority came to power, they have waged a wholesale attack on our health-care system.”

About 52 million adults under 65 could have been excluded from buying individual health insurance under the pre-Obamacare rules, according to estimates from the Kaiser Family Foundation.

The DOJ’s new stance aligns with Texas and other conservative states that challenged the ACA. In December, a district court judge in Texas agreed with that position. The question is before the Fifth Circuit Court of Appeals.

The dispute could go to the Supreme Court, which has twice upheld much of Obamacare. Legal experts, including some who oppose the ACA, have said that they expect the courts to uphold the law.