The SDP was founded in 1990 following the Orchid Revolution in Manchuria that saw the collapse of the previous Marxist-Leninist regime by reformists within the regime. In 1990 they entered a coalition known as the Popular Front for Democracy and Revolution which governed until 1995 when Premier Du Changhao extended the Two-child policy which caused the SDP to walk out of government, effectively ending the Popular Front. Following the collapse of the Popular Front the SDP entered a de facto alliance with the social liberal Progressive Millennium Party. In 2000 they were unable to retain seats in the Zuigaohuiyi and in 2008 joined the PMP and Minzhudang to merge into the liberal New Progressive Party.