PDC leader José Napoleón Duarte was the mayor of San Salvador from 1964 to 1970, winning three elections during the regime of PCN President Julio Adalberto Rivera Carballo, who allowed free elections for mayors and the National Assembly. Duarte later ran for president with a political grouping called the National Opposition Union (UNO) but was defeated in the 1972 presidential elections. He lost to the ex-Minister of Interior, Col. Arturo Armando Molina, in an election that was widely viewed as fraudulent; Molina was declared the winner even though Duarte was said to have received a majority of the votes. Duarte, at some army officers' request, supported a revolt to protest the election fraud, but was captured, tortured and later exiled. Duarte returned to the country in 1979 to enter politics after working on projects in Venezuela as an engineer.