Platforms, in European politics, are openly organized political factions within left-wing political parties. Examples include the Republican Communist Network, the Workers Unity Platform and the Solidarity Tendency, platforms within the Scottish Socialist Party; the Socialist Workers Platform and the Committee for a Workers' International (International Socialists) platform, both Trotskyist platforms formerly within the Scottish Socialist Party and now part of Solidarity (Scotland); and the "plateformes" 1 through 4 of the Revolutionary Communist League (Ligue communiste révolutionnaire - LCR) in France.
Such groups in American left-wing political organizations are usually called tendencies or caucuses.
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Platform (European politics) Wikipedia(Text) CC BY-SA