A professor of political economy at Sofia University from 1910 onwards, he took a leading role in the overthrow of the government of Aleksandar Stamboliyski in 1923 and was chosen to head the coalition that succeeded the deposed premier. The coup was able to succeed as the Bulgarian Communist Party took a neutral attitude towards the Agrarians rather than supporting Stamboliyski. He became Prime Minister of Bulgaria on 9 June that same year and continued in the role until 4 January 1926. During that period he was the leader of the Democratic Alliance. His premiership was marked by deep internal struggles with the Bulgarian Communist Party, which Tsankov repressed mercilessly, declaring martial law and outlawing the Communists in 1925 following an attempt on Tsar Boris's life and a bomb attack on the St Nedelya Cathedral. His actions led to Comintern denouncing the government as a "victorious Bulgarian fascist clique", whilst he later turned his attentions on the Agrarian Peoples Union, who were also suppressed, albeit less ferociously