Wyoming Senate candidate Liz CheneyElizabeth (Liz) Lynn CheneyHouse GOP pushes non-nuclear sanctions after Trump decertifies Iran deal Senate to consider resolution rolling back Obama-era land rule House passes bill to block Obama land planning rule MORE's (R) opposition to gay marriage is drawing criticism from her lesbian sister.

Cheney, running against Sen. Mike EnziMichael (Mike) Bradley EnziGOP senators ask Trump for meeting on biofuels mandate Senate budget just the latest attack on seniors Week ahead: GOP's next steps on tax reform | Fed chief speculation heats up | Senate to vote on disaster relief MORE (R-Wyo.), reiterated on Sunday morning that she doesn't support gay marriage. That drew rebukes from Mary Cheney and her wife, Heather Poe.

Poe took to Facebook to rip Liz Cheney for her comments.

"I was watching my sister-in-law on Fox News Sunday (yes Liz, in fifteen states and the District of Columbia you are my sister-in-law) and was very disappointed to hear her say "I do believe in the traditional definition of marriage," she says in a Sunday afternoon post.

"Liz has been a guest in our home, has spent time and shared holidays with our children, and when Mary and I got married in 2012 — she didn't hesitate to tell us how happy she was for us. To have her now say she doesn't support our right to marry is offensive to say the least."

Mary Cheney shared that post, and added her own criticism.

""Liz — this isn't just an issue on which we disagree — you're just wrong — and on the wrong side of history," she writes.

Liz Cheney said Sunday morning that she loves Mary and Heather "very much. ... This is just an issue on which we disagree."

Liz Cheney is in a tough spot on the issue. A socially conservative outside group run by former Arkansas Gov. Mike Huckabee's (R) daughter has been airing ads accusing her of supporting gay marriage. She's responded by saying she believes the issue should be left to the states and that she personally opposes allowing same-sex couples to marry, a position at odds not only with her sister but with her father, former Vice President Dick Cheney (R), who supports gay marriage.

A recent poll released by the outside group opposing Cheney found her trailing Enzi by more than 50 points in the race.

— This post was updated at 5:55 p.m.