News about a current lawsuit against Obamacare has come out within a few days of news about an old one from which it grew. The Donald Trump administration put itself on record urging the courts to strike down the entire Affordable Care Act. And a new book by Supreme Court reporter Joan Biskupic revealed details about the curious path that Chief Justice John Roberts took in the 2012 case.


In that case, the nine justices of the Supreme Court split into four blocs.


Four of the Republican appointees — Samuel Alito, Anthony Kennedy, Antonin Scalia and Clarence Thomas — voted to strike down the law’s requirement that nearly everyone buy health insurance, to strike down its expansion of Medicaid because it coerced state governments, and to strike down the whole law as a result. Two Democratic appointees, Ruth Bader Ginsburg and Sonia Sotomayor, voted to uphold everything. Two other Democrats, Stephen Breyer and Elena Kagan, voted to uphold the coverage requirement but modify the Medicaid expansion to give states more freedom.


Roberts made up a bloc of one. He ruled that the coverage requirement could be reconceived as a tax on people without insurance, and therefore upheld; the Medicaid expansion had to be modified; and the rest of the law could stand.


In all, seven justices voted against the law’s Medicaid provision, which was therefore modified; five voted to strike down a legal requirement to buy insurance; five voted to uphold a tax on the uninsured; and five voted to uphold the rest of the law. Roberts was the only one in the majority on all counts, and his opinion was the controlling one.


We have long known that Roberts’s initial inclination was to strike down the coverage mandate, period, and that he changed his mind. What Biskupic explains is that when the justices privately shared their initial views after oral argument, Roberts sided with the liberals on the Medicaid question. Also, she writes that Roberts always wanted to preserve most of the law — whether because he thought on principle that the court should make the most limited ruling possible or because he feared the political consequences for the court of making an expansive ruling.


According to Biskupic’s account, originally Roberts tried to persuade Kennedy to strike down the mandate while leaving the rest of the law in place. But Kennedy did not budge in believing that if the mandate went, the law would have to go with it. Roberts then came up with his compromise ideas on the mandate (upholding it as a tax) and on Medicaid (modifying it), and selling Breyer and Ginsburg on the second point.


Assuming Biskupic has these details right, it raises many questions about Roberts’s thought process. Why did he change course when he failed to bring Kennedy on board for upholding the law minus the coverage mandate?


He could have voted with the Republicans to strike down the mandate and with the Democrats to uphold the rest of the law. That course would have left him isolated as the only justice to take his precise mix of views; but that’s where he ended up anyway.


Why did he need to bring Kagan and Breyer around on Medicaid, and why did they feel it worthwhile to do so? Perhaps they wanted to modify the Medicaid provisions of the law to give conservatives a partial win to soften their disappointment at the upholding of most of the law. But he could, again, have served as a swing vote on his own.


Biskupic’s story makes it sound as though Roberts, and to a lesser extent Breyer and Kagan, engaged in unseemly politicking without much relation to constitutional logic. It doesn’t sound much like Roberts’s confirmation-hearing promise to “call balls and strikes” based on the legal merits of a case.


But if you read it carefully, the account is compatible with Roberts’s changing his mind about those merits. And in any case, his opinion in the case has to stand or fall on the force of its arguments about the law.


In the current case, opponents of Obamacare are challenging the law on the basis that Congress, in 2017, got rid of the tax on people who go without insurance. The opponents’ theory, endorsed by one judge, is that if the coverage mandate was saved only by relabeling it a tax and then the tax was eliminated, the provision has to be struck down; and if it is struck down, the rest of the law has to be nullified, too, since Congress would not have adopted it without the provision.


It is a screwy case. By choosing to eliminate the tax without touching the rest of the law, Congress in 2017 separated the issues, and the courts, one would think, should follow its lead.


But Biskupic’s story about Roberts’s handling of the Obamacare case seven years ago tells us something more about today’s challenge. It suggests that Roberts is reluctant to move against Obamacare even when considering a case that he thinks has real legal merit.


How likely is he to vote to strike down the law in this case, when he has given us no reason to think he considers it credible?


Ramesh Ponnuru is a Bloomberg Opinion columnist. He is a senior editor at National Review, visiting fellow at the American Enterprise Institute and contributor to CBS News.