Missouri Gov. Eric Greitens resigned Tuesday amid both criminal and legislative investigations that stemmed from an extramarital affair and questions about campaign financing. Greitens, a sometimes-brash political outsider whose unconventional resume as a Rhodes scholar and Navy SEAL officer made him a rising star in the Republican Party, resigned Tuesday amid a widening investigation that arose from an affair with his former hairdresser. The 44-year-old governor spent nearly six months fighting to stay in office after the affair became public in January in a television news report that aired immediately following his State of the State address. The probes into his conduct by prosecutors and lawmakers began with allegations stemming from the affair and expanded to include questions about whether he violated campaign-finance laws. Greitens said his resignation would take effect Friday. “This ordeal has been designed to cause an incredible amount of strain on my family — millions of dollars of mounting legal bills, endless personal attacks designed to cause maximum damage to family and friends,” he said in a brief statement from his Jefferson City office, his voice breaking at times.