The effect could be seismic. Expansion is expected to make 200,000 more people eligible for state-run coverage in July, pump billions of dollars into the health care system with them and supercharge state budget discussions about how to pay for it all next year.

After years of watching Republican leaders reject Medicaid expansion at the Capitol, Missourians went to the polls in August and overruled them with 53 percent of the vote.

The effect could be seismic. Expansion is expected to make 200,000 more people eligible for state-run coverage in July, pump billions of dollars into the health care system with them and supercharge state budget discussions about how to pay for it all next year.

But first, it has to survive the Supreme Court.

A week after Election Day, justices are set to hear arguments from 18 Republican attorneys general, including Missouri’s, on why the Affordable Care  Act, which enables expansion, should be struck down.

And if they prevail, expansion and other ACA reforms, including protections for people with pre-existing conditions, would be null and void here.

The law survived the court once, in 2012, with conservative Chief Justice John Roberts joining the four liberals to save it.

But this new case could be one of the first heard by a new 6-3 conservative majority bolstered by Judge Amy Coney Barrett, President Trump’s nominee to replace liberal icon Ruth Bader Ginsberg.

And Sidney Watson, a St. Louis University law professor who focuses on health care issues, said that could make a big difference in whether some or all of the law survives.

“The risk to the law is greater with Justice Ginsburg gone,” she said in an interview. “This case is really in play now.”

The facts of the case  

The case itself, titled California v. Texas, is effectively a targeted attack on a potential weak spot in the law, one Republicans created when they cut taxes in 2017.

That weak spot is known as the “individual mandate,” the part of the health care law that required most Americans to buy health insurance or pay a tax penalty.

When Republicans went to the Supreme Court wanting the law struck down eight years ago, one of the arguments made was that the mandate was unconstitutional and that made the law unconstitutional, too.

The court disagreed, saying Congress could create the penalty under its taxing power.

But the new lawsuit says that when Republicans in Congress changed the mandate penalty to $0 in the 2017 tax cut bill, the mandate lost its status as a tax, and with that its protection under the 2012 decision.

Like last time, Republicans are arguing that if the mandate goes down, the whole law should, too.

That kind of result could send shockwaves through the health care system.

Tim McBride, a health care economist at Washington University in St. Louis, said researchers have estimated somewhere between 18 million to 20 million people could become uninsured.

“It would be really disruptive,” he said.

But the plaintiffs say they have to do their jobs.

“Simply put, the Affordable Care Act is unconstitutional,” Missouri Attorney General Eric Schmitt said in a statement. “And, while fixing the law is in the hands of Congress, my job is to protect and defend the Constitution of our State and the Land. That is a charge I promise to continue to lead."

Reading the tea leaves

Of course, the court doesn’t have to agree with Schmitt and the other plaintiffs.

Watson, the St. Louis University law professor, thinks some disagreement is likely.

“Most lawyers and scholars looking at this are saying that is just way too far overboard to strike down the whole law,” she said.

For example, Yale law professor Abbe Gluck recentlywrote an essay for SCOTUSBlog— a court-watcher favorite — pointing out that two conservative justices have shown distaste for striking down entire laws over one bad provision.

Chief Justice John Roberts, for example, voted to leave the Consumer Financial Protection Bureau in place even as he ruled that a part of the law that created the agency was unconstitutional.

And Justice Brett Kavanaugh, a Trump nominee, did something similar in another case where he wrote that “constitutional litigation is not a game of gotcha against Congress, where litigants can ride a discrete constitutional flaw in a statute to take down the whole, otherwise constitutional statute.”

Judge Barrett, Trump’s latest nominee, is seen as more skeptical becauseshe wrote an essay in 2017 saying Roberts “pushed the Affordable Care Act beyond its plausible meaning to save the statute” in 2012.

“Had he treated the payment as the statute did—as a penalty—he would have had to invalidate the statute as lying beyond Congress’s commerce power,” Barrett wrote then.

But if Roberts and Kavanaugh stayed consistent with a more surgical approach, they and the three liberals would have a majority to save the law — and Missouri’s Medicaid expansion.

That’s not a no-drama guarantee either, though.

Watson, the St. Louis law professor, said the individual mandate was closely linked to requiring insurers to cover people with pre-existing conditions without extra charges, so a decision nominally saving the law could still cut that.

The Kaiser Family Foundation estimated there were a little more than 1 million Missourians with declinable pre-existing conditions —30 percent of non-elderly adults — as of late 2019.

The court of public opinion

The Supreme Court will take some time to decide the case after oral arguments, though.

In the meantime, Democrats seeking office in Missouri and across the country are running on protecting former President Barack Obama’s signature domestic policy regardless of what the justices decide.

Rich Finneran, the Democrat looking to unseat Schmitt as state attorney general this fall, says he would drop out of the lawsuit if elected.

“The lawsuit is a totally inappropriate use of taxpayer dollars to try to take away health care protections from the people of Missouri, especially after the vote we took in August to expand Medicaid,” he said in a recent interview.

Democratic State Auditor Nicole Galloway is also using the lawsuit in her run against Republican Gov. Mike Parson, who appointed Schmitt as attorney general after Josh Hawley won a U.S. Senate seat.

“Governor Mike Parson and his hand-picked Attorney General Eric Schmitt are in court suing to gut protections for the millions of Missourians with pre-existing conditions,”Galloway’s website reads.

(Parson’s campaign says he also supports protections for pre-existing conditions and helpedintroduce two bills this year to enact them, though neither got very far.)

And while neither candidate could restore the law entirely if the justices rule on the side of the plaintiffs, Democrats could feasibly do so if they win a Senate majority and the White House this fall.

Joe Biden, the Democratic nominee for president, has made “protecting and building on Obamacare” a centerpiece of his campaign.

And shortly after Trump nominated Barrett last weekend, Biden's campaign cast Trump as another Republican coming after their health care.

“Even now, in the midst of a global health pandemic, the Trump Administration is asking the U.S. Supreme Court to overturn the entire law, including its protections for people with pre-existing conditions," he said in a statement.

Congressional Republicans are touting their own fixes, too.

Sen. Josh Hawley, who as Missouri attorney general signed on to the lawsuit in the first place, noted he’s co-sponsored three bills that could help.

“Congress should act now and adopt the legislation I have introduced and cosponsored to lower insurance costs, get the price of prescription drugs down, and protect people with pre-existing conditions,” he said in a statement. “The Supreme Court may rule any number of ways, but the Senate doesn’t have to wait on that outcome. We can and should act now.”

It’s not clear how quickly they’ll act, though. The three bills were referred to committee last year and have not moved since.