 The OSP was shunned by other leftwing parties, because of its strong opposition to the social-democratic SDAP and the Communist CPH.Cooperation with the small Left-Communist RSP led to their merger with the RSAP in 1935.The OSP is very comparable to other parties formed as orthodox Marxist opposition within social-democratic parties, like Independent Social Democratic Party of Germany - see anti-Stalinist left and centrist Marxism.