Социалистическая народная партия
Initially called the Mayority Popular Socialist Party, the party was formed after a split in the Popular Socialist Party. The split had emerged in the PPS following the 1975 gubernatorial elections in Nayarit. In 1976 the opponents of the PPS party leadership had formed the 'National Committee to Defend the Popular Socialist Party' in Tepic. The Committee called for the holding of a 'Fifth National Assembly' of the party, which constituted the Mayority Popular Socialist Party as a separate party. The new party claimed to represent the original political line of PPS formulated by Vicente Lombardo Toledano. The group that had formed the trade union centre UGOCM-Roja joined PPM.