Attorneys representing 20 Republican state officials on Wednesday will walk into court and ask a federal district judge to invalidate the Affordable Care Act a move that could unleash chaos on insurance markets and, eventually, leave an estimated 17 million Americans without coverage.

Its an outlandish request that relies on what even the laws longtime critics are calling an outlandish argument. Jonathan Adler , the Case Western law professor who was an architect of the last big lawsuit challenging the Affordable Care Act s constitutionality, says the cases theory is unmoored and absurd . Lamar Alexander, the Tennessee Republican and chairman of the Senates health committee, has called it far-fetched .

But while the case seems unlikely to prevail, defenders of the law and advocates for the people who depend on it arent ready to dismiss the threat out of hand. And its easy to see why, given not just the stakes but also the circumstances of Wednesdays hearing.

The plaintiffs filed their suit in U.S. District Court in Fort Worth, Texas, where they knew they would get a conservative jurist and where they drew Reed OConnor , a George W. Bush nominee.

The last time an issue related to the Affordable Care Act landed in OConnors courtroom was in 2016, when he blocked Obama administration regulations that would have prohibited health care providers from refusing to treat transgender patients for religious reasons. That ruling probably had more to do with his feelings about religious freedom and LGBTQ rights than the Affordable Care Act, but nobody walked away thinking he was a fan of the law, the people who wrote it or the ideas behind it.

Meanwhile, the Texas case has already taken one unexpected, but critical, turn. In June, the Trump administrations lawyers at the Justice Department filed a brief supporting the lawsuit. Customarily, Justice Department lawyers defend federal statutes, even ones that the administration in power doesnt like, in order to meet the presidents constitutional obligation that the laws be faithfully executed.