Sleževičius was elected to the Lithuanian parliament, initially the Constituent Assembly, later the Seimas, on four occasions. In 1926, as a representative of the Lithuanian Popular Peasants' Union, Sleževičius became the prime minister for a third time. His government introduced important changes aimed at normalizing the situation in Lithuania, but the reforms faced resistance from the Catholic clergy, military officers and the parliamentary opposition. The resistance culminated in a military coup d'état in December 1926, which brought to power the authoritarian rule of Antanas Smetona. Sleževičius continued participating in the activities of his party but never again regained his previous influence.