R. Clarke Cooper, the executive director of the gay GOP group Log Cabin Republicans, has called on Rick Santorum, Mitt Romney and Newt Gingrich to repudiate a pledge from the National Organization for Marriage (NOM) each signed promising to work against gay marriage.

The GOP presidential candidates signed the group's 5-point pledge last summer.

In on op-ed published Tuesday by the Washington Times, Cooper criticized recent revelations that the group was working on a strategy to pit minorities against supporters of marriage equality.

“NOM put explicit plans to exploit racial divisions on paper,” Cooper wrote. “'The strategy goal of this project is to drive a wedge between gays and blacks.' Regarding immigrants, 'We must interrupt this process of assimilation by making support for marriage a key badge of Latino identity.' NOM's ultimate agenda? 'Fanning the hostility' between LGBT Americans and racial minorities.”

“Before the Iowa caucuses, Republican presidential candidates, including Governor Mitt Romney, rightly chose to reject a marriage pledge sponsored by a group called The Family Leader because the organization appealed to racial division. The NOM marriage pledge signed by Mitt Romney, Rick Santorum and Newt Gingrich should be similarly repudiated now.”

(Related: Maggie Gallagher defends anti-gay marriage group's race-baiting memos.)

GOP presidential hopeful Fred Karger has also called on his rivals to disavow the pledge.

NOM has previous gone after Texas Rep. Ron Paul for not signing its pledge, which asks signers to support a federal constitutional amendment banning gay marriage, defend the Defense of Marriage of Act (DOMA) in court, appoint judges and an attorney general who will “respect the original meaning of the Constitution,” appoint a presidential commission to investigate the “harassment of traditional marriage supporters,” and back legislation that would allow a ballot question on the issue for voters of the District of Columbia.

(Related: NOM tapped Rep. Steve King to spearhead Iowa gay marriage repeal effort.)