The Radical Civic Union (Spanish: Unión Cívica Radical, UCR) is a social liberal political party in Argentina. The party has been ideologically heterogenous, ranging from classical liberalism to social democracy. The UCR is a member of the Socialist International. Founded in 1891 by radical liberals, it is the oldest political party active in Argentina. For many years the party was either in opposition to Peronist governments or illegal during military rule. The UCR's main support comes from the middle class. Throughout its history the party has stood for free elections, supremacy of civilians over the military and liberal democratic values. Especially during the 1970s and '80s it was perceived as a strong advocate for human rights.