Mexico's new President Andres Manuel Lopez Obrador waves from his car while heading toward the Congress for his inauguration, in Mexico City, Mexico December 1, 2018. REUTERS/Daniel Becerril

MEXICO CITY (Reuters) - Veteran leftist Andres Manuel Lopez Obrador was sworn in as Mexican president on Saturday, heralding a historic shift to the left in a country struggling to overcome gang violence, chronic poverty and disillusionment with the political class.