This book exposes in broad strokes the development of the Mexican left, its moments of unity and rupture, its differences in political strategy, its defeats and triumphs, its debates and regroupings, its social and electoral growth, its blurring and regroupings. , his resistance against the policies of the ruling class and its collaborationism, his search for democracy and socialism and his electoral participation in the presidential succession of 2012. It is an exercise in organizing historical memory to contribute to the knowledge of who, from different leftist perspectives, have sought for many years the democratic and socialist transformation of Mexico.