Following the death of Únzaga, the mainstream of the FSB came under the leadership of Mario Gutiérrez. the party's candidate in the 1960 elections. Following the return of the military to power in the aftermath of the 1964 coup d'état, it was the MNR's turn to be repressed, and FSB's fortunes seemed to be on the rise again. The FSB now sought to ally itself with an emerging Christian democratic tendency and focused its attentions on organising in the Santa Cruz Department. As aprt of the Christian Democratic Community it endorsed General Bernardino Bilbao Rioja's candidacy in the 1966 Presidential election although René Barrientos of the ruling faction won easily. With Congress closed in 1969 the FSB descended into in-fighting, with a leftist FSB-Izquierda (FBSI) splitting off in 1970.