Between the fall of the Berlin Wall in November 1989 and the election in March 1990 , the old Social Democratic Party was re-established as a separate party , while the rest of the SED lost a lot of members and renamed itself the Party of Democratic Socialism ( PDS ) at a special party meeting in December 1989 . The rump of the SED that remained was renamed as the Party of Democratic Socialism ( PDS ) at a special party congress in December 1989 .