Before this week, the well-being of tens of millions of Americans was at stake in the lawsuits challenging the Affordable Care Act.

Now something else is at stake, too: The legitimacy of the Supreme Court.

Nobody knows how the justices will rule. And nobody can know, not even the justices themselves. On Friday morning, perhaps by the time you read this, they will meet privately to take their first vote. More often than not, this first vote determines the final verdict. But there are exceptions and Anthony Kennedy, on whose decision the outcome presumably depends, has a reputation for long deliberation and changes of heart—particularly in major cases like this one.

That’s good. With the result apparently in doubt—smart money still says the chances of the full law surviving are about 50-50—Kennedy should think long and hard about how he wants the Court to rule. So should Chief Justice John Roberts, who appeared more skeptical of the government’s case during oral arguments but nevertheless indicated that he, like Kennedy, understood the government’s premise—that health care was a special market, perhaps requiring special intervention.

If that concern is not enough to sway the chief justice, than perhaps his frequently professed concern for the court’s respectability will.