Presidential hopefuls Michele Bachmann, Mitt Romney and Rick Santorum have pledged to work against marriage equality.

Candidates signing the National Organization for Marriage's (NOM) 5-point pledge promise to support a federal constitutional amendment banning gay marriage, defend the Defense of Marriage Act (DOMA) in court, appoint judges and an attorney general who will “respect the original meaning of the Constitution,” appoint a presidential commission to investigate the “harassment of traditional marriage supporters,” and back legislation that would allow a ballot question on the issue for voters of the District of Columbia.

NOM announced the three candidates had signed on to their pledge just days before launching its Values Voters Bus Tour, which will make 22 stops in 4 days starting on Monday en route to the Iowa Straw Poll in Ames.

“We are grateful to Michelle [sic] Bachmann, Mitt Romney and Rick Santorum for their courage and their leadership in standing up for marriage, and so are millions of Americans who care about protecting marriage,” NOM President Brian Brown said in a statement.

“Marriage is an issue with an unbroken string of victories that unites Republicans, and we're pleased and honored the leading candidates in the race for the GOP nomination have spoken up for marriage,” Brown added. “We expect the voters of Iowa, New Hampshire and South Carolina will continue rewarding candidates who champion marriage.”