WASHINGTON — Fresh off some of his most triumphant days in office, President Donald Trump has expanded his attack on the Affordable Care Act, a move that has baffled Republicans and Democrats alike.

On Monday night the Trump administration reversed its position on a legal challenge to the Affordable Care Act. After formerly arguing that only some of the act is unconstitutional, Trump’s Justice Department is now arguing the entire 900-page law should be thrown out. This would end popular, bipartisan provisions, such as the ban on denying insurance to people with pre-existing health conditions.

“The Republican Party will be the party of health care,” Trump announced to reporters during a visit to the Capitol on Tuesday. He then urged Republican senators in a closed-door meeting to revisit efforts to repeal and replace Obamacare, according to people in the room.

Many are puzzled why Trump would make this move, especially so soon after Attorney General Bill Barr announced that the Robert Mueller investigation concluded his campaign did not conspire with Russia during the 2016 presidential election. Though the full report has not been made public, Trump has claimed total vindication and declared victory over his critics.

In contrast, the anti-Obamacare lawsuit and the pre-existing conditions debate have been nightmares for Republicans. Pre-existing conditions became one of the main lines of attack for Democrats during the 2018 midterms, and even Republicans concede it worked. Democrats signaled they are happy to take up that fight again in the 2020 election cycle.

“It’s hard to figure out,” said Sen. Chris Murphy. “They literally are teeing this up as an issue for Democrats for the next year and a half. They’re not even making a laughable attempt to save the most popular parts of the Affordable Care Act.”

Senate Minority Leader Chuck Schumer called the legal position “a two-year anchor around the neck of every Republican.”

Republican reaction was all over the map. Some stood behind the president and said the lawsuit will force Congress to take up health care reform again. Senior Sens. Chuck Grassley and John Cornyn said the new position doesn’t matter because the courts, not Trump, will ultimately decide the lawsuit. Sen. Susan Collins of Maine expressed her “dismay” at the administration’s position and called it “very disappointing.”

Senate Health Committee chairman Lamar Alexander called the White House's position "a dubious legal theory and we won't know for a long time whether it succeeds."

Others punted. House Minority Leader Kevin McCarthy said he couldn’t comment because he hadn’t read the legal argument through yet; the administration’s position filed to the 5th Circuit Court of Appeals is one paragraph long. Sen. Cory Gardner, who represents the swing state of Colorado, also said he hasn’t had a chance to read it. Asked for her reaction, Alaska Sen. Lisa Murkowski simply said “no.”

Launched by 20 Republican state attorneys general, the lawsuit argues that the entire ACA was rendered unconstitutional when Congress repealed the individual mandate tax penalty last year. In December, US District Judge Reed O’Connor agreed with the states in a ruling that has been widely criticized by legal experts. Democratic attorneys general appealed the ruling and it is now before the 5th Circuit Court of Appeals.

The Trump administration had previously argued some elements of the ACA, such as expansion of Medicaid to millions of low-income people and allowing children to stay on their parents’ health insurance plans until the age of 26, should be preserved. But on Monday, the Department of Justice switched positions and stated that O’Connor’s ruling should be upheld.

Republicans say the lawsuit will not lead to an end in pre-existing condition protections because Congress would be forced to pass a new law to replace the ACA before that happened. Last week at a rally in Ohio, President Trump once again railed against the late Sen. John McCain for casting the decisive vote to kill Obamacare repeal in 2017. Trump said that McCain badly hurt the Republican Party, and “we would have ended up making a great health care plan, frankly, with the Democrats because they would have had no choice.”

Democrats ridiculed that notion. Republicans failed to agree on an Obamacare replacement plan when they held control of Congress and the White House. To pass a new bill, they would need to go through not just Trump and Senate Majority Leader Mitch McConnell, but House Democrats led by Speaker Nancy Pelosi.

“If there is a Republican proposal for how to replace the Affordable Care Act and still provide protections for most Americans that they’ve come to rely on, they need to put it on the floor,” said Sen. Chris Coons.