The Christian conservative group The Family Leader is asking GOP presidential candidates to pledge their opposition to gay marriage.

The group's CEO, Republican Bob Vander Plaats, will unveil The Marriage Vow: A Declaration of Dependence Upon Marriage and Family at a press conference on the west steps of the Iowa state capitol building on Thursday at 11AM.

According to Fox News, the pledge includes support for the Defense of Marriage Act (DOMA), the 1996 law that bars federal agencies from recognizing the legal marriages of gay and lesbian couples, opposition to gay marriage laws, picking constitutionalists for federal judgeships and opposition to Sharia law. Candidates are also being asked to pledge fidelity to their spouses.

Vander Plaats spearheaded last year's successful ouster from the bench of three Iowa Supreme Court justices after the 7-judge panel unanimously ruled in favor of gay marriage proponents in 2009. The group has also lobbied lawmakers to approve a constitutional amendment that would reverse the court's decision. The effort died earlier this year in the Democrat-controlled Senate after passage in the House.