Facing new calls to resign from some fellow Republicans, Missouri Gov. Eric Greitens instead affirmed his intent Tuesday to remain on the job while seeking forgiveness for an extramarital affair that he described as a "personal mistake.". David Petraeus, the national-security golden-boy who rose from commander of CENTCOM to head of the CIA (and was often mentioned as a potential future GOP presidential candidate), has reportedly resigned, citing an extramarital….