During his emigration, Horák participated in activities of social democracy in exile (in 1948 the party was forcibly merged with Communist Party). After the Communist Party lost its power (1989), he returned to Czechoslovakia and re-established the party, becoming its leader. During the 1990 election, the party failed to obtain seats in the parliament; Horák also got involved in internal party disputes. In the 1992 elections, the party narrowly obtained parliamentary presence. In 1993, Miloš Zeman replaced Horák as party leader.