Answer
Mamadou Dia was Senghor's long-standing associate. They worked closely together in the Senegalese Democratic Bloc (BDS), a political party they co-founded in 1948. Dia served as Senegal's first prime minister from 1957 to 1962, during which time he implemented a number of economic and social reforms. He was later imprisoned by Senghor after a political dispute in 1962, but was eventually released in 1974.