Businessman Herman Cain has said that he is suspending his campaign for the Republican presidential nomination to avoid news coverage that is hurtful to his family.
Mr Cain's announcement came five days after an Atlanta-area woman claimed she and Mr Cain had an affair for more than a decade, a claim that followed several allegations of sexual harassment against the Georgia businessman.
Mr Cain, whose wife stood behind him on the stage, made the announcement before several hundred supporters gathered at what was to have been the opening of his national campaign headquarters.
Mr Cain had surged in polls until news surfaced in late October that he had been accused of sexual harassment by two women during his time as president of the National Restaurant Association in the 1990s.
Mr Cain said: "Now here's why it hurts - because my wife, my family and I, we know that those false and unproved allegations are not true. So one of the first declarations that I want to make to you today is that I am at peace with my God. I am at peace with my wife. And she is at peace with me."
Whether Mr Cain would stay in the race or drop out was the subject of speculation throughout the week. Even some top supporters who had spoken with him arrived unsure what he would say.
Mr Cain returned to his suburban Atlanta home on Friday and met with his wife. It was the first time they have seen each other face to face since 46-year-old Ginger White came forward on Monday, and said she and Mr Cain had carried on a 13-year relationship.
Mr Cain has denied having an affair with her. He said the concern over the toll the allegations were having on his family as well as a candid assessment of whether his campaign could still attract the needed support would inform his decision on whether to press ahead.
Mr Cain has denied wrongdoing in all cases.
The main beneficiary of Mr Cain's fall has been former speaker of the US House of Representatives Newt Gingrich, who has risen steadily in polls nationally and in early voting states. Mr Gingrich has emerged as the main challenger to fellow front-runner Mitt Romney in the Republican race to take on President Barack Obama next year.