President Obama's Organizing for Action (OFA), a group of major backers in the president's reelection bid, is lending its muscle to the fight for equal marriage in Illinois.

OFA fired off a letter to supporters in the president's home state March 19 asking them to contact their state reps. in favor of the bill.

The group has partnered up with Illinois Unites for Marriage, a coalition of pro-LGBT groups headed up by Lambda Legal, the American Civil Liberties Union of Illinois and Equality Illinois.

In the email, OFA urges supporters to look up their state reps. and call them.

"Like President Obama said last year, he believes that marriage equality is a question of fairness — of treating others the way you want to be treated," the email reads. "Right now, his home state is just one step away from becoming the 10th state in the nation to approve same-sex marriage — and making sure that gay and lesbian families in Illinois are treated equally in the eyes of the law."

The president has already voiced his support for the Religious Freedom and Marriage Fairness Act.

The bill passed the Illinois Senate but has yet to face a House vote. The measure needs 60 votes to pass, and reports from LGBT groups suggest that the bill does not yet have the support it needs. The bill could face a vote this week, but LGBT leaders have speculated that a vote after representatives return from spring break on April 8 is more likely.