That raised the possibility that Roberts jumped to join the court's liberals at the last moment because he got more out of them in the way of compromise than he could from Justices Anthony M. Kennedy, Antonin Scalia, Samuel A. Alito Jr., and Clarence Thomas.
"It seems quite plausible that initially there were five votes to strike it down, so Roberts came around to a compromise position," said Kermit Roosevelt, professor of constitutional law at the University of Pennsylvania Law School.
The court isn't insulated from the political world. Someone once observed, in weighing the susceptibility of judges to political pressure, that courts read election returns.
In Bush v. Gore, the court not only read the election returns, but cast judgment on them. With Democratic court appointees lining up behind Al Gore and Republican appointees deciding the dispute in favor of George W. Bush, the idea that the court was politics by other means gained popular currency.
But that isn't the way the court typically does business. Justices run a gauntlet of academic and legal challenges before they make it to the high court. They tend to be cerebral and reserved. Yes, they have an ideological standpoint, but their secluded and cloistered world is the antithesis of the carnival atmosphere and rough and tumble of politics.
They're simply not that crass.
I've interviewed Justices Stephen G. Breyer and Thomas, and had casual backyard conversations with Roberts. Each spoke of the need for the courts to do everything in their power to preserve institutional credibility.
They can't appropriate money, and they don't have an army or a police force. Their credibility is the only thing they've got.
"The justices exist in a sphere that is different from politics," said Stephen Engel, a partner at Dechert L.L.P., the University City-based law firm and a former clerk for Kennedy. "The nine of them and their small staffs work in something of a marble temple."
Roberts was named to the court by Bush, himself under pressure to name a reliable conservative to the court.
Roberts mostly lived up to that billing until Thursday. Much of the argument in the case centered on the government's power to require citizens to purchase health insurance or pay a financial penalty under the Commerce Clause of the Constitution. Roberts rejected that line of analysis in an opinion that dismayed some liberal legal scholars.
But he reached the same result by concluding that what the Obama administration had called a penalty was a tax. The government's taxing power is unquestioned. Case closed.
That reading gave conservatives fits, and may be questionable. Taxes are controversial and typically are raised to support government operations, not to cause individual citizens to purchase a product.
Yet Roberts also was faced with the challenge of preserving institutional authority.
Coupled with the court's extreme reluctance to overturn duly enacted legislation, it may be that Roberts decided discretion was the better part of valor.
The health care plan is anathema to conservatives as both law and policy. It accords the federal government sweeping new powers to compel citizens to purchase a product that they might not have otherwise, and in that analysis opens the door for further intrusive actions. It is, in the view of many conservatives, a bureaucratic Rube Goldberg machine that is not paid for and sets up the state as a super-parent, giving things away to citizens.
It is possible that Roberts agreed with all of that. In the majority opinion, he suggests the law might well be bad policy. If so, he wrote, it is up to Congress to fix it, not the courts.
"It is going to send a message that this court is deciding cases not just on politics or ideology and that it is really committed to the law," said Robert Reinstein, constitutional law professor at Temple University Law School. "That will give it credibility for future decisions that may be more ideological."
When, no doubt, the political recriminations will begin again.
Contact Chris Mondics at 215-854-5957 or firstname.lastname@example.org