French political scientist Maurice Duverger drew a distinction between cadre parties and mass parties. Cadre parties were political elites that were concerned with contesting elections and restricted the influence of outsiders, who were only required to assist in election campaigns. Mass parties tried to recruit new members who were a source of party income and were often expected to spread party ideology as well as assist in elections.Socialist parties are examples of mass parties, while the British Conservative Party and the German Christian Democratic Union are examples of hybrid parties. In the United States, where both major parties were cadre parties, the introduction of primaries and other reforms has transformed them so that power is held by activists who compete over influence and nomination of candidates.