Can my spouse's credit score be affected?

I don’t know. I would ask an attorney or an accountant.

Is his name on the deed, note, or mortgage?

As long as her new husband was not on the loan for the property she is walking away from the foreclosure shouldn’t impact his credit. If she defaults on any credit she has jointly with her current husband, it will impact his credit. If your mom defaults on the mortgage for this property and the lender obtains a judgement against her, any real estate she owns – with or without her new husband – will be subject to a lien until the judgement is satisfied.

@SuperMouse, not every state allows a lender to go after a lendee for balances above the current resale value. In California, on a first trust deed they can’t go after you for another dime once they foreclose. Many Seconds were written as a home equity line of credit and those CAN go after assets once the property is foreclosed. Nevada is a whole different story. They can (and do) go after additional assets.