Updated

Building on the momentum of President Barack Obama's recent support of gay marriage, two major civil rights groups in his home state filed lawsuits Wednesday in hopes of legalizing same-sex marriage in Illinois.

The two lawsuits — brought by the American Civil Liberties Union of Illinois and the New York-based Lambda Legal — represent 25 couples statewide. Both challenge a state law that defines marriage as between a man and woman, arguing that the Illinois Constitution guarantees the right for same-sex couples to marry under due process and equality clauses.

"It's time for Illinois to recognize the love and commitment of these couples," said John Knight, director of the Lesbian, Gay, Bisexual, Transgender Project of the ACLU of Illinois. "We've waited long enough."

Knight said Obama's comments, as well as Gov. Pat Quinn's backing of gay marriage earlier this month and nationwide polls showing increasing public support for same-sex marriage set the stage.

The filings come a year after Illinois enacted civil unions, but many couples in the lawsuits said civil unions made them feel like second-class citizens.

Lambda Legal's lawsuit, which has 16 couples, includes Chicagoans Patrick Bova and Jim Darby. They've been together for 48 years and hope to marry by their 50th anniversary. They entered into a civil union last year, but said they want their relationship to be recognized in the same way as their heterosexual friends.

"I have bought so many toasters for so many weddings," Darby joked Wednesday at a news conference. "I want someone to buy me a toaster."

The 25 couples in both lawsuits tried to apply for marriage licenses in Cook County, but were denied.

It's unclear how Illinois will handle the cases' legal process, but attorneys with the advocacy groups are ready to take them to the state Supreme Court. The defendant named in the case, Cook County Clerk David Orr, is personally in favor of gay marriage. Several messages left for Cook County State's Attorney Anita Alvarez, who would represent Orr, were not immediately returned Wednesday.

A spokeswoman said Orr was out of the country and had not seen the lawsuit, but issued a statement on his behalf.

"The time is long past due for the State of Illinois to allow County Clerks to issue marriage licenses to couples who want to make that commitment," the statement said. "I hope this lawsuit clears the last hurdle to achieving equal marriage rights for all."

Currently, the District of Columbia and six states — Connecticut, Iowa, Massachusetts, New Hampshire, New York and Vermont — have legalized gay marriage. Courts decided for gay marriage in Massachusetts, Connecticut and Iowa. A lawsuit, filed by Lambda Legal, challenging an Iowa law that barred gay marriage prompted the Iowa Supreme Court to legalize it in 2009.

Legislation to eliminate language that prohibits gay marriage is pending in Illinois, but a vote isn't expected before the session is scheduled to end this week.

Illinois' civil unions give same-sex couples some, but not all, of the same legal rights and protections as marriage, such as the power to decide medical treatment for a partner and to inherit a partner's property. When that law was approved last year, opponents — including some religious and conservative groups — said it was a step toward gay marriage.

Republican State Rep. Mike Tryon, of Crystal Lake, voted against civil unions last year, and took a similiar stance on gay marriage Wednesday.

"I firmly believe that a marriage is between a man and a woman, and it should stay that way," Tryon said.

Some opponents also said the advocates were skirting what the public wants by taking it to the courts.

"Going around the will of the people is not the right way to change an institution that has thousands of years of history and is sound in its reasons for existing," said Peter Breen, executive director of the Chicago-based Thomas More Society. The public interest law firm opposes gay marriage.

Breen said the lawsuits would not hold up in court under the constitutional arguments and only a handful of states had succeeded in doing so.

However, Northwestern University political science professor Andrew Koppelman said the fact that both civil rights groups, which are selective about their cases, had stepped forward showed the lawsuits likely have a strong chance.

Lambda Legal is a national legal organization that advocates for the civil rights of homosexuals, bisexuals, transgender people and those with HIV. It and the ACLU share the same goal of legalization, but decided to pursue separate lawsuits because the groups have different missions. The lawsuits also slightly differ in legal reasoning.

Plaintiffs in the ACLU lawsuit, which includes nine couples, are Chicago police detective Tanya Lazaro and systems analyst Elizabeth Matos. The couple, who has been together 15 years and has two children, reject the notion of a civil union.

"It's not the same thing as a marriage. We want our relationship, our love and our commitment we've shown for 15 years to be recognized like everybody else's," Lazaro said. "When you're growing up, you don't dream of civil unions."

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Sophia Tareen can be reached at http://twitter.com/sophiatareen

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AP writer Shannon McFarland contributed to this report from Springfield.