Presidential hopefuls Michele Bachmann, Ron Paul, Rick Santorum and Herman Cain will address a forum sponsored by an anti-gay marriage group.

The four GOP candidates have agreed to take part in the Christian conservative The Family Leader's Thanksgiving Family Forum – A Family Discussion with the Republican Candidates, the group announced on Friday.

The Saturday, November 19 forum will be held at the First Federated Church in Des Moines, Iowa.

Also invited are Newt Gingrich, Mitt Romney and Rick Perry.

The Family Leader is Iowa's leading group working to repeal the state's gay marriage law with a constitutional amendment defining marriage as a heterosexual union.

Brian Brown, the president of the National Organization for Marriage (NOM), the nation's most vociferous opponent of gay marriage, praised the event: “The Thanksgiving Forum will elevate issues like marriage to the forefront of Iowans' minds and create the conversations necessary to help select the next President of the United States.”

(Related: Michele Bachmann, Rick Perry, Ron Paul, Herman Cain to address South Carolina anti-gay forum.)