Civil rights groups are preparing for what could be a long legal fight.

Thursday morning, the American Civil Liberties Union filed a class-action lawsuit. The group is trying to overturn a 2006 amendment to the Virginia Constitution banning same-sex marriage in the commonwealth.

In 2006, a clear majority of Virginians said they wanted to identify marriage in the commonwealth as strictly between a man and a woman, and it's now codified in the state constitution. But those involved in this lawsuit say the time is right to challenge Virginia law.

Victoria Kidd and her partner Christy Bergoff have been together for a decade. They have an 8-month-old daughter named Lydia. But their marriage license from Washington, D.C. is not honored in the commonwealth.

"The law doesn't recognize my relationship with Christy. By extension, the law doesn't recognize my relationship with Lydia," Kidd said.

They are one of two families listed as plaintiffs in the lawsuit filed in Federal District Court in Harrisonburg.

"It's the strongest effort we've made yet to strengthen families throughout Virginia," said Greg Nevins, an attorney at Lambda Legal.

The suit - filed by the ACLU, the ACLU of Virginia, and Lambda Legal - is seeking to overturn a six-and-a-half-year-old amendment in the Virginia Constitution that defines marriage as between a man and a woman. It passed easily on the ballot in 2006, with more than 57 percent of voters in support. But the ACLU says the measure is unconstitutional.

"We're now at the time where it's time to just ask the fundamental question: doesn't the federal Constitution mean we should all be protected and treated the same?" said Claire Gastanaga, executive director of ACLU of Virginia.

That's why these groups are taking their battle to court, a process that could take up to four years to wind through the legal system. Despite that, this family says it's in for the long haul.

"I don't want her to grow up with the idea that her parents are somehow less than anyone else, and that's what it's all about. That's what this case is all about," Kidd said.

Recent polling from Quinnipiac University less than a month ago shows 50 percent of Virginians support same-sex marriage in the commonwealth, versus 43 percent who oppose it.