The Supreme Court is expected to rule on the constitutionality of President Obama's landmark health care law as early as Monday.
A new Reuters poll shows that a majority of Americans oppose President Obama's health-care law-although they support most of its provisions, such as letting parents keep their children on their policies until age 26.
But 61% say they are against the "individual mandate," which forces Americans to purchase medical insurance.
The hot button campaign issue of immigration is also on the Supreme Court's docket, a widely watched judgement on Arizona's tough immigration law could be handed down sometime this week.
But it's the health-care decision alone that makes it the most important week of the campaign.
If the court rules against the law, political experts say it's hard not to see it as a rejection of a major part of Obama's first term in office.