McCain was still married and living with his wife in 1979 while aggressively courting a 25-year-old

McCain was still married and living with his wife in 1979 while, according to The New York Times' Nicholas Kristof, "aggressively courting a 25-year-old woman who was as beautiful as she was rich." McCain divorced his wife, who had raised their three children while he was imprisoned in Vietnam, then launched his political career with his new wife's family money. In 2000, McCain managed to deflect media questioning about his first marriage with a deft admission of responsibility for its failure. It's possible that the age of the offense and McCain's charmed relationship with the press will pull him through again, but Giuliani and Gingrich may face a more difficult challenge. Both conducted well-documented affairs in the last decade--while still in public office.

http://www.washingtonmonthly.com/features/2006/0607.benen.html