By Alex Dobuzinskis
(Reuters) - Former U.S. Vice President Dick Cheney entered the fray between his daughters over gay marriage on Monday as he rose to defend Liz Cheney, a Republican Senate candidate from Wyoming whose stance against same-sex nuptials has drawn barbs from her lesbian sister.
Liz Cheney said in an appearance on "Fox News Sunday" that she believes in "the traditional definition of marriage." She said she loves her sister Mary, who is in a same-sex marriage, but that "this is an issue in which we disagree."
That led to a quick response from Mary Cheney, who said on Facebook: "Liz -- this isn't just an issue on which we disagree -- you're just wrong -- and on the wrong side of history."
Liz Cheney is seeking to unseat incumbent Republican Senator Mike Enzi in a primary election in August 2014, and the gay marriage issue had already punctuated Cheney's campaign after the sisters clashed publicly over it in August.
The public spat comes as gays and lesbians seeking the right to marry have won a series of victories in the past year, with Hawaii last week becoming the 15th state to enact a law legalizing gay marriage and Illinois poised to become the next.
An increasing number of Republicans have come to support gay marriage, even though a solid majority in the party oppose it.
"This is an issue we have dealt with privately for many years, and we are pained to see it become public," Dick Cheney and his wife, Lynne, said in a statement on Monday.
"Since it has, one thing should be clear. Liz has always believed in the traditional definition of marriage. She has also always treated her sister and her sister's family with love and respect, exactly as she should have done," the Cheneys said.
Dick Cheney, who served as vice president under former President George W. Bush, has long indicated he was supportive of gay marriage, saying "people should be free to enter into any kind of relationship they want to enter into."
But he has said states should regulate the matter, not the federal government.
Liz Cheney, before announcing her candidacy for the U.S. Senate in July, served as a deputy secretary of state in the Bush administration. Her father was elected as a congressman from Wyoming in 1978 and served until 1989.
Her younger sister, Mary Cheney, married longtime partner Heather Poe last year. On Facebook, Poe said Liz Cheney has been a guest in the couple's home, spent time with their children and told them "how happy she was" for the two women when they wed.
Gallup released a survey in May finding that 53 percent of Americans believe the law should allow same-sex marriage. It was the third consecutive survey by the organization finding support of at least 50 percent for gay marriage.
While she opposes same-sex marriage, Liz Cheney had opposed a 2009 attempt to amend the Wyoming constitution to ban gay marriage and she supports extending health and other benefits to gay and lesbian couples.
As a result, political action committee the American Principles Fund has run a television advertisement against Liz Cheney accusing her of not being conservative enough.
(Editing by Leslie Adler)