The article deals with the analysis of current situation of the Mexican Left-Wing political forces following the triumph of Andrés Manuel López Obrador at the presidential elections of 2018. The author not only has researched thoroughly the correlation between the forces of different Mexican Leftist parties, but also is showing their evolution since the end of 1980s till the present time. The processes which are taking place inside the Leftist political forces are taken into consideration within the context of their historical evolution, the traditions and challenges which were and are customary to the Mexican leftists. A special focus is made on MORENA (which is currently the principal Leftist party) and its main predecessor and now - its competitor - the Party of Democratic Revolution. The article also contains some prognosis over the perspectives of Mexican Leftist movement.