If Barack Obama becomes President, he could join with House Speaker Nancy Pelosi to try and repeal the Defense of Marriage Act.
It's a federal law that prevents states from being forced to recognize same sex marriages performed in other states.
Obama openly calls for the repeal of DOMA, and has labeled it "an abhorrent law."
And at a recent news conference, Pelosi said she would support the repeal of DOMA if Obama becomes President.
Pelosi, who represents San Francisco, has always opposed the law. She was one of the few lawmakers to vote against it in 1996.
Obama used to support DOMA, but says he turned against it after hearing from homosexual friends who say the law has been hurtful to them.