WASHINGTON — If the Supreme Court strikes down the insurance mandate in the health care law, the justices will also have to decide how much more of the law should be invalidated, a potentially monumental decision that may affect other popular parts of the law.

Here are some questions that will likely arise:

Q: Why is this an issue?

A: The insurance requirement is widely viewed as critical to other consumer protections in the law, including the guarantee that everyone can get health insurance, even if they have a pre-existing medical condition.

Experts believe that it is nearly impossible to have such a guarantee without a way to induce younger, healthier people to get covered and offset the cost of insuring older, sicker ones.

Obama administration lawyers have asked the court to throw out the insurance guarantee if the justices decide the mandate is unconstitutional.

Q: Could any more of the law be stricken?

A: The court could decide to throw out the entire law, as a federal judge in Florida did last year.

The 26 states challenging the mandate and a host of other critics of the law have urged the justices to do that.

But few experts believe the court would take such a drastic step, which would entail striking many provisions that have nothing to do with the mandate, including new initiatives to boost public health, improve the quality of medical care and train more doctors and other medical professionals.

Q: Could the court just invalidate the mandate and keep everything else?

A: Yes. The 11th U.S. Circuit Court of Appeals — which is the only appellate court to strike the mandate — decided to do that, reasoning that the mandate is so weak that getting rid of it would not have much of an impact on even the insurance provisions in the law.