Four GOP presidential candidates have refused to sign a controversial marriage pledge, which asks them to support outlawing pornography, upholding the Defense of Marriage Act and creating a constitutional amendment banning same-sex marriage.

GOP frontrunner Mitt Romney as well as fellow candidates Tim Pawlenty, Jon Huntsman and Newt Gingrich have not signed the Family Leader’s Marriage Vow Pledge, but Michele Bachmann and Rick Santorum have.

Romney was the first GOP presidential candidate who refused to sign the pledge.