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The public war of words over same-sex marriage between former vice president Dick Cheney's two daughters escalated Sunday when Mary Cheney and her wife sharply criticized Liz Cheney for expressing clear opposition to same-sex marriage during a national television interview.

The back and forth was the latest round of a public split that has intensified in recent months. It comes as Liz Cheney is immersed in a heated campaign for the U.S. Senate in Wyoming, where her views on gay marriage have come under great scrutiny. It is also yet another instance of the Cheney family's views on marriage becoming enmeshed in politics.