Center-right party formed by 11 political organizations and dissidents who broke from the Bulgarian Communist Party led by Todor Zhivkov, the longest-serving leader within the Warsaw Pact and the longest-serving ruler in Bulgarian history. Party chose its leading dissident, Zhelyu Zhelev, as chairman. Zhelev became Bulgaria's first post-Soviet President from 1990 to 1997. SDS has been joined in coalition with GERB since 2019 and participates in elections as GERB-SDS. Party has been led by Rumen Hristov since 2018 [Съюз на демократичните сили (СДС); Romanised as Sayuz na demokratichnite sili (SDS)].