Ahdut HaAvoda
In 1944 he led the "Bet" Faction that split from Mapai and created the new "Ahdut HaAvoda" party. In 1948 he was one of the founders of the more pro-Soviet Mapam, and was elected to the first Knesset in 1949. In 1954 he resigned from Mapam along with Ahdut HaAvoda over the issue of relationships with the Soviet Union and remained the leader of Ahdut HaAvoda until the establishment of the Labor Party in 1968. He was reelected to the third Knesset in 1955.