Three prominent groups opposed to gay marriage are targeting the campaigns of three Republican congressional hopefuls over their support for such unions.

The National Organization for Marriage (NOM), FRC Action and CitizenLink said Thursday that they will mount a campaign against House candidates Carl DeMaio and Richard Tisei and Senate candidate Monica Wehby.

DeMaio, from California, and Tisei, from Massachusetts, are openly gay and have each endorsed marriage equality, though DeMaio has faced criticism in the past over placing a low priority on gay rights. In March, Tisei, who is married, skipped the GOP's annual state convention. In media interviews, he said attending the event would make it seem as if approved of the party's opposition to marriage equality.

Earlier this month, Wehby, who is looking to unseat Oregon Senator Jeff Merkley, released a television ad highlighting her support for same-sex marriage. According to, Wehby is the first Republican Senate candidate to run such an ad.

NOM President Brian Brown said he was “disappointed” by the candidates' stance on the issue.

“The Republican Party platform is a 'statement of who we are and what we believe.' Thus, the platform supports the truth of marriage as the union of husband and wife, and recognizes the sanctity and dignity of human life. This is what Republicans believe,” Brown said in a post announcing the campaign. “It is extremely disappointing to see Republican leaders in Washington help push the election of candidates who reject the party's principled positions on these and other core issues. We cannot sit by when people calling themselves Republicans seek high office while espousing positions that are antithetical to the overwhelming majority of Republicans.”

The groups pledged in a letter to top Republicans to “mount a concerted effort to urge voters to refuse to cast ballots for [the candidates] in the November election.”