It was formed when the followers of ex-Trotskyite Max Shachtman gained control of the old Socialist Party of America in the early 1970s. As a result of this takeover two dissident groups were formed; the Democratic Socialist Organizing Committee (which would later become the Democratic Socialists of America) and the reconstructed Socialist Party, USA.
Although most of SDUSA's members are Democrats, the organization has maintained ties with both major political parties and has, in the past, supported a strongly interventionist foreign policy.
Note: this party should not be confused with the earlier political party, the Social Democratic Party (USA)