(CNN) - Newt Gingrich stepped up his efforts to appeal to evangelical Christian voters in Iowa Monday by promising in writing to "defend and strengthen the family."
Gingrich, who has been married three times, specifically said he would "uphold the institution of marriage through personal fidelity to my spouse and respect for the marital bonds of others."
Gingrich made the pledge to The Family Leader, a socially conservative group based in Iowa. The organization has its own Marriage Pledge that other 2012 White House hopefuls have signed, including Texas Gov. Rick Perry, Minnesota Rep. Michele Bachmann and former Pennsylvania Sen. Rick Santorum.
Gingrich did not sign The Family Leader's pledge himself, but did provide a lengthy written response to the organization. The former House speaker said he was fully committed to defending traditional marriage, including enforcing the Defense of Marriage Act and supporting a constitutional amendment defining marriage as between a man and woman.
Gingrich also used his pledge to lambaste what he called an intrusion of federal courts in the private lives of Americans, saying the phenomenon "amounts to a constitutional crisis."
In a statement accompanying Gingrich's pledge, Family Leader President and CEO Bob Vander Plaats welcomed the former House speaker's commitment.
"We are pleased that Speaker Gingrich has affirmed our pledge and are thankful we have on record his statements regarding DOMA, support of a federal marriage amendment, defending the unborn, pledging fidelity to his spouse, defending religious liberty and freedom, supporting sound pro-family economic issues, and defending the right of the people to rule themselves," Vander Plaats said.
In November, the group said it had narrowed the list of candidates it might endorse to four: Gingrich, Perry, Bachmann and Santorum.
Political observers have long questioned Gingrich's appeal to socially conservative Christian voters because of his multiple marriages. The pledge made Monday came after Perry questioned Gingrich's marriages at a Republican primary debate in Iowa Saturday.
Perry warned that a politician who was unfaithful to his wife might also cheat in other ways, adding, "if you cheat on your wife, you'll cheat on your business partner, so I think that issue of fidelity is important."
Gingrich took the criticism in stride, saying "I've made mistakes at times. I've had to go to God for forgiveness. I think people have to measure who I am now, and whether I'm a person they can trust."