Clinton says Illinois should be the next in line to allow same-sex marriage. Delaware and Minnesota both legalized it recently.
Lawmakers are working to get it passed, but the sponsor has been shy a few votes so it hasn't been called up for a vote. Clinton says everyone needs to be treated equally under the law.
Governor Pat Quinn says he couldn't agree more. He's also urging the General Assembly to legalize same-sex marriage. He says the state has a chance to make history.
Opponents hope same-sex marriage doesn't become legal in Illinois. They say marriage should remain between a man and woman. Others argue civil unions should be enough.
Some experts say Clinton's support may make a difference and help encourage the House to pass the Marriage Equality Bill. It already passed the Senate in February.