 It is Bulgaria's second-largest party by membership.GERB is headed by Prime Minister of Bulgaria Boyko Borisov, the former mayor of Sofia, former member of the National Movement Simeon II and former personal guard of Todor Zhivkov in the 1990s.The establishment of the party followed the creation of a non-profit organization with the acronym (in Bulgarian) GERB — "Citizens for European Development of Bulgaria", earlier the same year.