The document summarizes the political history of Bihar, India in three periods: 1) Congress dominance from 1947-1967 when power was concentrated among upper castes, 2) Depleting Congress support from 1967-1989 as other parties gained traction, and 3) Political ascendancy of backward castes from 1990s onward which led to the rout of Congress. Key events included the rise of Janata Dal and leaders like Lalu Prasad Yadav and Nitish Kumar who mobilized Dalits and Other Backward Castes, while the BJP attracted upper castes. Caste politics dominated Bihar's electoral landscape over these three periods.