A coalition of religious conservative groups will join forces the weekend prior to Thanksgiving to present “A Family Discussion With the Republican Candidates” at a Des Moines church. Four of seven candidates have confirmed their participation. In an email message sent Friday to supporters, Bob Vander Plaats , chief executive of The Family Leader , explained that the organization’s purposefully chose the weekend before Thanksgiving “in the hope of giving Iowans something to discuss at the Thanksgiving dinner table.” Working with The Family Leader, which is the political action arm of the state’s Family Research Council affiliate, are the National Organization for Marriage, a religious conservative organization devoted to opposing civil marriage for gays and lesbians, and CitizenLink, the national political arm of Focus on the Family