 Complete the following phrase:  Gustavo Francisco Petro Urrego ; born April 19, 1960 is a Colombian politician, ex guerrilla member and a presidential candidate who previously served as mayor of Bogotá. A left-wing politician, Petro was a member of the revolutionary group M-19 in the 1980s. The group later evolved into the Alianza Democrática M-19, a political party in which Petro participated as a member of the national congress in the 1990s. Petro served as a senator as a member of the Alternative Democratic Pole party following the 2006 legislative elections with the second largest vote in the country. In 2009, he resigned his position to aspire to the presidency of Colombia in the 