WASHINGTON (AP) - Demonstrators are back on the sidewalk outside the Supreme Court, where justices today are hearing arguments on the key part of the health care overhaul bill -- the requirement that Americans purchase health insurance.

Yesterday, the justices signaled that they are willing to rule on the constitutionality of the law -- seeming to reject arguments that a ruling would be premature because nobody is yet paying a penalty for not having health insurance.

Opponents believe it is unconstitutional to require Americans to buy health insurance. The administration believes the law is valid.

Today is day two of three days of arguments.

Virtually every American will be affected by the outcome, due this summer in the heat of the presidential and congressional election campaigns.