As governor, he overhauled the state's education system and served as chairman of the National Governors Association. Clinton was elected president in 1992, defeating incumbent Republican opponent George H. W. Bush. At age 46, he became the third-youngest president in history. In 1978, Clinton entered the Arkansas gubernatorial primary. Clinton was only 32 years old when he took office, the youngest governor in the country at the time and the second youngest governor in the history of Arkansas. Due to his youthful appearance, Clinton was often called the 'Boy Governor'. Clinton won the 1992 presidential election (370 electoral votes) against Republican incumbent George H. W. Bush (168 electoral votes) and billionaire populist Ross Perot (zero electoral votes), who ran as an independent on a platform that focused on domestic issues. Bush's steep decline in public approval was a significant part of Clinton's success. Clinton's victory in the election ended twelve years of Republican rule of the White House and twenty of the previous twenty-four years.