If the Supreme Court decides that Congress exceeded its constitutional authority in enacting the part of the law that requires most Americans to either have health insurance starting in 2014 or pay a penalty, does that invalidate the rest of the law? And if not, how much, if any, of the rest of the law should it strike down?

With the question on Day 1 being whether the Supreme Court can even take up the issue of whether President Obama's health care law is constitutional, NPR's Nina Totenberg saw "a bunch of justices groping for a way to get to the merits of this case."

On Day 2 of the sessions about the constitutionality of the health care overhaul, there were many tough questions for the government's lawyer. But it wasn't absolutely clear where the majority will come down, NPR's Nina Totenberg says.