The MSZDP is a member of the Socialist International made peace in 1921 with Miklós Horthy's government. The MSZDP leadership entered as part of an unsuccessful post-war socialist administration into government. Counter-revolution and Revolution resulted in a brutal backlash. Many MSZDP supporters were killed during the White Terror. The environment became increasingly hostile during activity and the Second World War. The leadership of Anna Kéthly took a prominent role in Imre Nagy's Provisional Government.
MSZDP and The MSZP were for the same left-wing support in competition. The results of the 1990 elections was a huge disappointment to the MSZDP. The Social Democratic Party participated as Schmuck's new party in the 2014 general election. László Kapolyi died after a long illness on 2014 11 29. Party President László Kapolyi was elected MP, MSZP, parliamentary group. Party merged to Socialist Party of Hungary Gyula Peidl, disbanded Anna Petrasovits. Végül az MSZP Szabolcs-Szatmár-Bereg megyei listájának második helyéről került be a parlamentbe. A gyanú szerint akaró Kapolyi László biztatására kötötte az erőmű előző.