Some of its most prominent leaders were Patxi Iturrioz, Eugenio del Río, Rosa Olivares Txertudi, Milagros Rubio, Jesús Urra Bidaurre and the brothers Javier and Ignacio Álvarez Dorronsoro.
EMK joined in 1975 the Democratic Convergence Platform, a coalition created by much of the opposition, led by the Socialist Party (PSOE), to fight against Francoist Spain.
For the first legislative elections of 1977 EMK made a coalition with Euskal Iraultzarako Alderdia (EIA) called Euskadiko Ezkerra (EE) candidate Patxi Iturrioz took a few months the only parliamentary seat obtained in the elections, following the resignation of Francisco Letamendia[3] Also, in Navarre EMK, EIA, OIC-EKE and ORT formed the electoral coalition Navarrese Left Union (UNAI), that was the third most voted party in Navarre (9.47%), but failed to gain any seat.
On April 2, 1983 EMK became independent organizationally from the Communist Movement (MC), to explore new political spaces, which led the organization to support the coalition Auzolan, comprising Liga Komunista Iraultzailea (LKI), LAIA and Nueva Izquierda (Euskadiko Ezkerra split).
After the electoral defeat of Auzolan, EMK began a joint campaign with the trotskyist formation LKI, adopting a pro-abertzale speech and asking several times to vote for HB, which has led some historians to believe that the party became a satellite of abertzale coalition.