Hillary Rodham Clinton on Saturday reiterated her support for the Equality Act and warned that her GOP presidential rivals will try to undo nationwide marriage equality, if elected.

Progress on LGBT rights “can be undone,” Clinton told a gathering of Human Rights Campaign (HRC) volunteers ahead of the group's 19th annual National Dinner, which was headlined by Vice President Joe Biden.

(Related: Joe Biden: Americans have moved past homophobia.)

“We're going to face some ridiculousness, especially from our friends in the GOP,” the Democratic presidential candidate said. “Believe what they say.”

Clinton specifically targeted Texas Senator Ted Cruz and former Arkansas Governor Mike Huckabee, who have been vocal in their support for Kim Davis, the elected clerk of Rowan County, Kentucky who is fighting to prevent her county office from issuing marriage licenses to gay and lesbian couples. Cruz and Huckabee stood next to Davis as she emerged from a 5-day jailing for refusing to comply with the Supreme Court's ruling striking down gay marriage bans in all 50 states.

(Related: Vatican: Pope Francis' meeting with Kim Davis not a form of support.)

“[It can be hard to believe that it gets better], especially when you turn on the TV and you see a Republican candidate for president literally standing in the court house door in Kentucky, calling for people to join him in resisting a Supreme Court ruling, celebrating a county clerk who's breaking the law by denying other Americans their constitutional rights,” Clinton said.

Clinton's endorsement of the Equality Act was welcomed with loud applause from the audience.

“Congress must pass the federal Equality Act,” she said. “That law would finally outlaw discrimination against LGBT people. … It's a great, noble piece of legislation that deserves to become the law of the land. As president, I will fight for it. And I hope many of you will be with me when I sign it into law.”