RSP(B) joined the UDF, the alliance in Kerala which is led by the INC.
The party won 2 seats in the state assembly, Shibu Baby John and Babu Divakaran, in the 2001 election.
Babu Divakaran became the Minister of Labour in the state government.
In 2005 RSP(B) left UDF, a decision largely attributed to the party general secretary A. V. Thamarakshan.
Thamarakshan decided to break the alliance and go alone in the 2016 Kerala assembly elections.