Marianne Gingrich may threaten her ex-husband's ambition of becoming the President, just as he's making a final surge in South Carolina. In a tell-all interview with ABC, the former speaker's 2nd wife claims, 'he wanted an open marriage and I refused.' Gingrich allegedly asked his 2nd wife to share him with a Congressional aide, all while skewering President Bill Clinton for his own extra-marital affairs. The Former speaker also allegedly called Marianne to say goodnight while sleeping next to his mistress Callista. Gingrich vehemently denied the allegations, erupting at CNN's John King for asking about it during Thursday's GOP debate, and criticizing the national media for focusing on the interview. The debate also put Mitt Romney on the defensive about his refusal to release tax returns. Gingrich's checkered marital past has been raised just as he is vying for the evangelical Christian vote in South Carolina. Some recent polls show Gingrich in a near tie with frontrunner Mitt Romney..