The Trump Justice Department’s position in a lawsuit seeking to strike down the Affordable Care Act is putting congressional Republicans in a weird spot.

If the Justice Department is successful in the case, the entirety of the Affordable Care Act will be struck down, just as the 2020 campaign season is getting into full swing. Republicans’ failed attempt at repealing the Affordable Care Act in 2017 was a disaster, and helped Democrats take the House in 2018. The Senate GOP has shown no interest in trying again to find a replacement, even as the threat of this lawsuit looms.

Making the whole situation even more awkward for congressional Republicans is that the legal challenge is being pushed on the basis of their 2017 tax bill that eliminated Obamacare’s individual mandate. And the Justice Department’s arguments rely, in part, on a legal theory the GOP previously endorsed in a 2012 Supreme Court case that sought to take down the law.

“It’s an absurd argument,” Sen. Susan Collins (R-ME) said. “If Congress had wanted to strike down the rest of the Affordable Care Act, it would have done so. It chose not to.”

While the lawsuit is still considered a long shot, the Justice Department didn’t make congressional Republicans’ lives any easier by abruptly changing its position in its case; the Trump administrtion had previously argued that only the pre-existing condition protections should been invalidated, but in court briefs filed Wednesday evening, the Trump administration is now arguing that the whole law should go down.

The Justice Department’s rationale have been derided by legal experts across the spectrum as “lunacy,” “nuts” and “an empty unprincipled mess.” Its logic is convoluted, but the basic argument is this: By reducing the individual mandate penalty to $0, Congress robbed the mandate of its revenue producing function that allowed the Supreme Court to uphold it in 2012’s NFIB v. Sebelius. That makes the current $0 mandate penalty unconstitutional, and Congress knew this when it passed the 2017 tax bill.

The Justice Department then blames Congress for not making more it clear that it no longer thought the mandate was “essential” to the preexisting conditions protections, a finding made by a previous Congress.

The Justice Department said additionally that allowing the rest of the law to stand “would create an insurance market quite unlike the one that Congress intended, with potentially serious consequences for the stability of the market.”

The reaction, among Senate Republicans, to this interpretation of their tax bill vote was, at best, mixed.

TPM could find only one Senate GOPer defending the DOJ position: Sen. Josh Hawley (R-MO), who said arguing for the whole law’s invalidation seemed to him a “more rational” position than arguing that only the pre-existing conditions protections be struck down.

Hawley was not in Congress when it took its tax bill vote in 2017; he was, however, the attorney general in Missouri when it joined Texas in challenging the law in the current case.

Other Republicans said they agreed with the argument that mandate is unconstitutional. Finance Chairman Chuck Grassley (R-IA) called it “legitimate,” even as he was skeptical the challengers would ultimately win — while stopping short of supporting the view that the whole law should come down because of their tax bill.

“Those of us who believed that [mandate] was unconstitutional at the time, depending how you construct the legal argument, would have thought therefore it makes the whole thing unconstitutional, so it’s not inconsistent,” Sen. Rob Portman (R-OH), an architect of the 2017 tax bill, said. “But that’s not what we thought was going to happen at that time [of the 2017 tax bill vote]. We thought we would get rid of a mandate that a lot people didn’t like.”

More Republicans still said outright that they disagreed entirely with the rationale the Justice Department was offering.

Sen. Lamar Alexander (R-TN), who chairs the committee that oversees the Department of Health and Human Services, called the Trump administration’s theory “far fetched— particularly the idea that anybody intended to get rid of the pre-existing conditions protections.”

“There was specific statements made by different members of the Republican side that this is not to impact coverage of pre-existing conditions,” Sen. Bill Cassidy (R-LA) told TPM. “So clearly if you take the comments of those voting [for] it, it was anticipated it might be an issue and it was rejected as something that was desirable.”

Sen. Roy Blunt, a member of GOP leadership, said that the mandate provision in the 2017 bill was “intended to give people more options and be able to work more vigorously to find what those options are, and by removing the penalty, you allow people to make more choices, without being penalized for making those choices.”

This, coincidentally, is an argument Obamacare’s defenders are putting forward in the case and the Justice Department specifically rebuked it in its brief on Wednesday.