The New York City mayor urged voters to support Question 6 while a new poll suggested the measure is losing favor among African Americans, a key constituency in Maryland.
The Supreme Court will decide at a private meeting on November 20 whether they will take California's Prop.
The case is one of several DOMA challenges the court has been asked to hear.
Alveda King, the niece of Martin Luther King Jr., can be heard on a new radio ad urging Marylanders to vote no on marriage equality in their state.
In a new ad opposing Minnesota's marriage discrimination amendment, Vikings punter Chris Kluwe harkens back to his attention-grabbing turn of phrase about what won't happen when same-sex couples get married.