Newt Gingrich is vowing never to commit adultery ever again.
"I pledge to uphold the institution of marriage through personal fidelity to my spouse and respect for the marital bonds of others," the Republican frotnrunner just wrote in a letter.
Gingrich's adulterous past is a hot topic on the campaign trail. He had an affair with current wife, Callista, while he was married to second wife Marianne. And he told first wife Jackie he was leaving her when she was recovering from cancer treatment.
During Saturday's debate, Rick Perry said, "If you will cheat on your wife, if you will cheat on your spouse, then why wouldn't you cheat on your business partner, or why wouldn't you cheat on anybody for that matter?"
Perry and other Republican candidates have already signed the "marriage vow," put forward by an Iowa conservative group called The Family Leader.
Meantime, Gingrich's top rival, Mitt Romney, is deploying his wife of 42 years, Ann, to draw a sharp distinction between him and Gingrich.
Ann is stepping up her appearances on the campaign trail, telling women in Iowa, "He is there, he is steadfast. You can count on him. He won't abandon you in the hardest times."
Political analyst Hank Sheinkopf told INSIDE EDITION, "Family values matter a lot and the best way to show family values is show off your family, show off your wife, take the marriage vow and say, 'Well, you know what? No one's better married that we are.' "
For her part, Callista Gingrich is never far from her husband's side, always perfectly groomed.
Pultizer Prize-winning columnist Robin Givhan writes in today's Daily Beast: "Her style is painstakingly starched from head to toe. If she were to slouch, she just might crack."
"She is an absolute asset to Newt Gingrich who needs again and again to remind voters at Republican presidential primaries in a lot of states that are very conservative, that he's a happily married man," said Sheinkopf.
Here's how Ann Romney and Callista Gingrich stack up.
Ann is 62 years old and has five sons and 16 grandchildren. A former stay-at-home mom, she was afflicted with multiple sclerosis 10 years ago.
Callista is 45 years old. She's a devout Catholic. Gingrich, raised a Lutheran, converted to Catholicism.