Every legal challenge to the Affordable Care Act (ACA) has, in some sense, also been a political challenge. Republicans, unable to either repeal or replace the health insurance reform bill, have chosen instead to put their backs into the fight against it in the courts.

And with the exception of a win and a draw against the birth control benefit, those efforts have been resounding failures. The U.S. Supreme Court has twice upheld large portions of the law, rejecting conservatives’ claims it is unconstitutional. Based off oral arguments Tuesday in Republicans’ latest efforts to upend the law, it appears as though Chief Justice John Roberts will get a third chance to uphold Obamacare. 

This latest attack before a three-judge panel of the Fifth Circuit Court of Appeals centers on Republicans’ claims that their 2017 tax reform bill gives the courts no other option but to strike as unconstitutional the entirety of the health law due to its individual mandate provision. 

According to Republicans, the individual mandate has two distinct parts to it. The first part “mandates” people carry health insurance by use of the word “shall.” The second part imposes a tax on those people who fail to purchase insurance. In 2017, Republicans left the language of the mandate in place, but zeroed out its tax penalty for those who don’t carry insurance.

Republicans argue the Supreme Court ruled that the individual mandate was an appropriate exercise of Congress’ power to tax in National Federation of Independent Business (NFIB) v. Sebelius, the first case to uphold the ACA. And because the tax from that mandate is now zero, they say, the tax isn’t really a tax anymore. And if a tax isn’t a tax, then the mandate is no longer constitutional and must be struck along with the entire rest of the ACA.

Does your head hurt yet? It should. It’s an argument the Court explicitly rejected in NFIB, noting that the ACA doesn’t attach any negative consequences for failing to comply once that penalty has been paid. In other words, individuals ultimately maintained a choice in complying with the ACA: Purchase insurance or pay a tax. The fact that Congress decided to make that tax zero doesn’t fundamentally change the nature of that choice. 

Or it shouldn’t. But as I said before, the legal attacks on the ACA have always been political attacks, and none more so than this one.

Never a party to be deterred by a little thing like a Supreme Court loss or public disapproval—see their campaigns against abortion rights and marriage equality, for example—Republicans have pressed on with this latest and most preposterous attack on the ACA anyway. Let’s be clear, this isn’t just an attack. Republicans are asking the courts to effectively repeal the law. 

And that’s precisely what makes this case so dangerous. So far, the courts have been the last firewall against the political attacks on the ACA. Even some of the law’s most strident critics laughed off these latest legal claims as preposterous. But Republicans didn’t bring this case in just any federal court. They went before Judge Reed O’Connor, who has made it a habit to rule against any policy initiative from the Obama administration. In December, O’Connor delivered for them, issuing a sweeping opinion striking down the entire law. On Tuesday, a panel of judges on the conservative Fifth Circuit Court of Appeals appeared ready to affirm O’Connor’s ruling—not based on the strength of the legal arguments, but on fundamental partisan opposition to the bill. 

Should that happen, it would be up to the Roberts Court to step in to quite literally help save lives. Otherwise, the 12 million Americans receiving insurance through the ACA’s Medicaid coverage will see that coverage gone. As would the nearly 133 million Americans who rely on the law’s protections for preexisting health conditions.

That’s just a terrifying fraction of what is at stake here. 

It could be months before the Fifth Circuit issues its decision. Depending on the timing, it’s possible the case will wind up before the Supreme Court next term: against the backdrop of a presidential election, and with Chief Justice John Roberts once again called on to decide the fate of Obamacare.