The 1969 split in the Congress Party stemmed from the Congress Syndicate's dominance. This influential group of senior leaders opposed Indira Gandhi's leadership, her efforts to centralize power, and her assertion of greater control. These tensions culminated in a party division, creating two factions: Congress (O) and Congress (I), with Indira Gandhi heading the latter. Therefore, the primary cause was the Dominance of the Congress Syndicate.