A Texas judge “correctly held” that Obamacare’s individual mandate to hold insurance is inseparable from the rest of the law, the Trump administration told an appeals court Wednesday in arguing the entire program must fall.

The Justice Department’s brief solidified President Trump’s support for a lawsuit that could decimate his predecessor’s signature health program, even though Republicans haven’t reached consensus on a replacement.

It’s also a change of heart.

Administration lawyers once took a limited view of the state-driven challenge, saying a narrow slice of Obamacare should be struck after Congress decided to zero out the penalty for shirking insurance as part of the GOP tax overhaul.

They changed course after the lower court sided with state Republicans who say the tweak made the entire program unconstitutional, including its protections for sicker Americans, subsidies for private coverage and sweeping expansion of Medicaid in dozens of states.

“In the district court, the Department of Justice took the position that the remainder of the ACA was severable, but upon further consideration and review of the district court’s opinion, it is the position of the United States that the balance of the ACA also is inseverable and must be struck down,” Justice attorneys wrote to the U.S. Court of Appeals for the Fifth Circuit.

If upheld on appeal, the case would force Washington to revisit health reform. Yet any decision that wipes away Obamacare’s sweeping benefits could politically injure the GOP in the middle of the 2020 campaign.

Despite that risk, red states that filed the lawsuit in 2018 urged the appeals court to affirm the Texas ruling from December.

“The district court correctly recognized all this in declaring the ACA unlawful in its entirety,” the states said in their own brief Wednesday. “The Department of Justice now agrees — and so too should this court.”

Blue-state attorneys general and House Democrats are fighting back in the appellate courts. They say the challenge before the Fifth Circuit is misguided, because Congress intentionally left the rest of Obamacare alone when it attacked the individual mandate.

They also stress the potential consequences of striking down the entire law, since millions gained coverage under its most popular provisions.

For his part, Mr. Trump thinks the Supreme Court will strike down Obamacare in the end.

He recently said it would clear the way for the GOP to repeal and replace the law after their embarrassing failure in 2017.

Senate GOP leaders said they have no intention of revisiting the issue, however — for one thing, Democrats control the House. That forced the president back off from his nascent push and punt a repeal vote until after the 2020 elections.

Some Democrats are looking beyond Obamacare and proposing a sweeping, government-run plan known as single-payer health care or “Medicare for All,” citing the nearly 30 million who remain uninsured despite the 2010 law.

The Congressional Budget Office on Wednesday released a laundry list of complexities for drafters of a single-payer plan to consider, such as government’s role in administering the plan and funding it, who would be eligible for coverage and whether enrollees must pay a share of costs.

Architects of the system would also have to figure out whether private insurers could exist alongside the government plan, or if they’d be relegated to covering things like cosmetic surgery.

“Establishing a single-payer system would be a major undertaking that would involve substantial changes in the sources and extent of coverage, provider payment rates, and financing methods of health care in the United States,” the CBO wrote.