 It was to no avail; as expected, the PDS was heavily defeated by the Alliance for Germany, a centre-right coalition dominated by the East German branch of the CDU and running on a platform of speedy reunification with West Germany.A "grand coalition" of the Alliance and the revived Social Democrats elected the CDU's Lothar de Maizière as Prime Minister on April 12.Following negotiations between the two German states, a Treaty on Monetary, Economic, and Social Union was signed on May 18 and came into effect on July 1, among things replacing the East German mark with the "Deutsche Mark" (DM).