From the moment the White House decided it would defend no part of the Affordable Care Act in a federal lawsuit brought by 20 red-state governors and attorneys general, Democrats pounced on the real-world implications.

The lawsuit claimed that Congress’s removal of the individual-mandate penalty for not having health insurance nullified the entire law and made it unconstitutional. The Trump administration’s refusal to stand up for any part of the law meant that if a judge ruled against the law, the whole thing would come crashing down, including the popular parts, namely coverage protections for Americans with preexisting health conditions.

Leading up to the midterm elections, Democrats were unrelenting in their attacks on Republicans over the future of the ACA’s preexisting conditions policy. It became such a focal point of their campaigns that Republicans had to start talking about it, too, promising voters they would save the protections. Even one of the attorneys general on the lawsuit, Missouri’s Josh Hawley, cut an ad in which he talked about his sick son and the importance of covering people with current or past health problems.

President Trump, in campaign rallies around the country, started declaring himself and the Republican Party the best on the issue of preexisting conditions.

Late Friday night, on the last night of open enrollment, a Texas judge ruled in the lawsuit that the ACA was unconstitutional and the whole law should be overturned. Nothing happens to the law yet; this decision will be appealed and is likely to end up before the Supreme Court, but it certainly puts President Barack Obama’s signature policy accomplishment in a perilous situation.

The big question facing Republicans is whether they will support legislation that protects people with preexisting conditions. Throughout the campaign, Democrats pointed out what they called the hypocrisy of Republicans supporting the lawsuit while also telling voters such protections would be preserved. The problem with that promise is that Congress has not put in place any safeguards or contingencies for those protections in the event the law gets overturned.

Several Republicans, in the weeks leading up to the election, introduced legislation forbidding insurance companies to discriminate against the 133 million Americans with health problems. But some of those proposals left loopholes that would have allowed companies to deny coverage or charge more based on gender or age. Moreover, there’s risk in requiring companies to cover sick people if the rest of the law isn’t in place. To work, the law needed younger, healthy people to balance out the insurance pool. But without a mandate or subsidized plans, those people are less likely to buy coverage, leaving insurance companies with a sicker, and thus expensive, consumer base.

Politically, it’s a nightmare for Republicans. Democrats, after eight years on the defensive when it came to the ACA, have found themselves with the upper hand. Recent polling by the Kaiser Family Foundation found that 65 percent of Americans consider it “very important” to keep insurers from denying people coverage based on their health. Republicans have yet to pass a replacement for the ACA, something they’ve been promising for years.

After the news of the judge’s decision broke, House Minority Leader Nancy Pelosi (D-Calif.), the presumptive incoming speaker, immediately declared her intention to protect people with preexisting conditions. The onus would then be on Senate Majority Leader Mitch McConnell and his Republican caucus to do the same.

Trump, who tweeted about the ruling, said Congress must pass a law that protects preexisting conditions. But this is health policy in divided government (remember: “Nobody knew health care could be so complicated”), and it’s not going to be so easy to replace the ACA if the Supreme Court strikes it down.