Colombians have elected a new president. Gustavo Petro, 62, is set to become the first leftist in the country's top job. The former rebel of the now defunct M-19 movement beat millionaire businessman Rodolfo Hernandez in Sunday's election. Petro will take the oath of office in August, replacing the deeply unpopular Ivan Duque. For analysis, we speak to Gerard Martin, a political sociologist based in Medellin, Colombia.