A conservative super PAC is taking to the airwaves with a new commercial criticizing Republican Senate candidate Liz Cheney's comments on gay marriage.

Cheney said earlier this year that she is "strongly pro-life and I am not pro-gay marriage." The ad, from the American Principles Fund, suggests that Cheney isn't sufficiently conservative on the latter issue. It singles out comments Cheney made on MSNBC in 2009 in opposition to a constitutional ban on gay marriage and in support of a State Department decision to extend benefits to same-sex couples.

"MSNBC: The go-to network for Barack Obama and Washington's liberal elites. So what's Liz Cheney doing here?" asks the narrator of the ad.

The group is airing the ad statewide in Wyoming for about two weeks, according to spokeswoman Sarah Huckabee Sanders, the daughter of former Arkansas governor Mike Huckabee. She did not respond to questions about how much money the group is spending to air the ad.

Cheney, daughter of former vice president Dick Cheney, is challenging Sen. Mike Enzi (R) in a campaign that has already grown heated. A spokesperson for Cheney swiftly criticized the new super PAC ad.

"This is a dishonest smear by an out-of-state super PAC," said Cheney spokesperson Kara Ahern. "The people of Wyoming deserve better."

Cheney's sister Mary Cheney is a lesbian who publicly criticized her sister's position against gay marriage, calling it "dead wrong" in an August Facebook post.

The American Principles Fund was formed this year, according to campaign finance records. Through the end of June, the group had raised about $54,000, all from a single donation from Sean Fieler, head of Equinox Partners, a hedge fund. Fieler has made substantial contributions to the National Organization for Marriage, a group opposing gay marriage.