Rick Perry on Monday became the latest GOP candidate to sign The Family Leader's anti-gay marriage pledge, the Des Moines Register reported.

Perry joins Minnesota Representative Michele Bachmann and former Pennsylvania Senator Rick Santorum in signing the Iowa-based Christian conservative group's controversial The Marriage Vow: A Declaration of Dependence Upon Marriage and Family, which was first unveiled in July.

The move comes two days after Perry joined five other candidates at a Family Leader forum in Iowa.

(Related: Rick Perry reiterates support for gay marriage ban, opposition to gay adoption.)

The pledge asks presidential candidates to “vigorously” oppose marriage equality, be faithful to his or her own spouse, vow to protect women and children from pornography and reject Sharia law because it is a “form of totalitarian control.” The group, influential among social conservatives, has said it would not endorse any candidate that does not sign the pledge.

The Family Leader, which is headed by Bob Vander Plaats, drew heated criticism for including the passage that an African-America baby born into slavery in 1860 was more likely to be raised in a two-parent household than after the nation elected its first African-American president. The passage was removed, but not before Bachmann and Santorum endorsed the two-page document.

The 14-point pledge also ironically asks candidates to have “Respect for the marital bonds of others,” and footnotes in it suggest that being gay is a choice that may have a negative impact on public health.

Former New Mexico Governor Gary Johnson called the pledge “offensive and unRepublican” and “nothing short of a promise to discriminate against everyone who makes a personal choice that doesn't fit into a particular definition of 'virtue.'”

GOP strategists Doug Gross described Perry's move as a late in the game Hail Mary pass.

“This one probably won't work since he is appealing to the same voters as are a number of the other candidates when he should be focusing on a core group who don't want Romney and have no where else to go,” Gross told the Register.