The effects of Judge O’Connor’s ruling, if upheld, could be devastating, including a sharp rise in the number of uninsured and a substantial weakening of coverage guarantees.

This is a repeat of what happened in 2010 and 2013, as long-shot challenges to Obamacare that were once largely academic gained traction in the lower courts. And, with that, something else happened: Politicians began rallying behind the lawsuits. The media covered the cases. Legal academics debated and wrote about the disputes. The public started paying attention. Before long, the cases slithered their way to the nation’s highest court.

Rinse, repeat.

Jack Balkin, a professor at Yale Law School, calls this the off-the-wall/on-the-wall theory of constitutional change. “The history of American constitutional development, in large part, has been the history of formerly crazy arguments moving from off the wall to on the wall, and then being adopted by courts,” Mr. Balkin wrote in an article in The Atlantic in 2012, as the Supreme Court was readying its first big ruling on Obamacare.

In Mr. Balkin’s view, the reason that seemingly bizarre legal arguments reach the mainstream is that politicians and others in power get behind them. Yes, support from the academy or from social movements moves the needle as well. But it is only when political actors — parties, elected officials, institutions — speak in favor of a position that it stands a chance of being taken seriously by the courts.

So it matters that attorneys general and officials from Texas and 19 other states brought the latest lawsuit. And that the Trump administration, which otherwise has a duty to defend duly enacted laws, agreed with the shakiness of their argument. Now a federal judge has given the green light, and Mr. Trump is loving it. Soon the Fifth Circuit will get a bite at the apple.

For now, nearly every actor with a stake in this controversy is in agreement that Obamacare should stay put while the ruling gets sorted out.

A day after the new ruling, Professor Balkin applied his off-the-wall/on-the-wall theory to the circumstances of this case. “I have seen this movie before,” he wrote in his popular legal blog, Balkinization. But he added that aside from victory laps from Mr. Trump and a few other Republicans, the response this time around is much more muted.